Knitting and so on: U-Turn Slippers

I'm back to knitting slippers again. As usual, I tend to prefer constructions that are a bit out of the ordinary (such as the Undecided Slippers I published last year).
These slippers are knitted in a U-Turn shape around the tip of your foot. They are constructed in one piece, i.e. there are only two ends to weave in per slipper. The pattern comes out best when using variegated yarn, e.g. colorful sock yarn.

This work by Knitting and so on is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Materials

3.25mm circular needles (even though everything is knitted back and forth)
about 40 grams of fingering weight yarn
a third needle for the three-needle-BO
tapestry needle to weave in ends
3 stitch markers
a safety pin to secure your stitch while turning the piece right sides out

Techniques & Notation

Judy's Magic Cast-On is a technique that gives you live stitches on both sides of your needle - it is generally used for toe-up socks (e.g. in this pattern), but it can be used for other purposes as well. Here's a written description (from Knitty) and here's a YouTube-video by Cat Bordhi and another YouTube-video by Very Pink Knits.
Picking up stitches from the side: Without your working yarn, insert the needle into the front leg of the edge stitch from back to front. A photo how this looks like, is shown in a post regarding the short wave mitts. Here’s a Knitty-article that explains picking up stitches in detail (also the difference between "picking up" and "picking up and knit"): http://www.knitty.com/ISSUEwinter04/FEATwin04TT.html
Three-Needle Bind-Off: https://youtu.be/Ph93jWSzTa0
Knitting a flat circle - or in case of this pattern a semicircle: The technique for knitting a flat circle has been described a few times on this blog, e.g. in the "Zoom Out Mitts"-Post. Basically it consists of doing 8 increases (evenly spaced out in one round) every other row, and varying the starting point for the first increase to avoid an octagon pattern.
In this pattern only a semicircle is knitted. This means that there will be only 4 increases on every RS row - and they will be started at a random stitch within the first quarter of the half circle.
In this pattern you will be asked to increase (or decrease) by 2 from one point in your knitting to another. This means that you can randomly distribute the increases (or decreases) between the two given points (stitch markers)
As an increase I used kfb and as decrease I used ssk, but you can use other stitches as well, e.g. a make 1 knit stitch (mk1) as increasing stitch or a k2tog as a decrease stitch.

Gauge and What You Need to Measure

I had a gauge of about 5 sts to 2 cm in width and 5 garter stitch ridges (10 rows) to 2 cm. With this gauge and with a CO of 2x18 sts, the cast on of the tip will be 8 cm long, The tip will grow by 1/4 of the circumference you measured. You can adjust the length of this part by casting on more or fewer stitches.
The pattern is written in a way that you can adapt it to the width and length of your feet. As an example I will give the numbers I had for my feet (in purple).
Before you start, measure around the widest point of your feet (i.e. the circumference) and the length of your feet.

Construction

The slippers is constructed in two parts - the tip and the heel. Both are knitted flat.
It is started at the sole of the tip by doing a magic cast on. Then you knit around that CO in a U-shape making semicircle increases at the tip until the straight egde is half as wide as the circumference of your feet. Then you basically knit the same rows you just knitted backwards, i.e. doing semicircle decreases until the two sides meet and join them with a three-needle bind-off.
To start the heel part, stitches are picked up and knit from the straight edge of the tip part. Then you knit back and forth until you start decreases for a round heel. After some decreases, you only work one side part until the two sides meet. Another three-needle BO closes the heel.
The picture on the right shows a slipper as seen from both the top and the side.

Instructions

Tip
CO 2x18 stitches with the magic CO (i.e. there are 18 stitches on each needle)

Now turn your needles around in a way that you're looking at the garter stitch bumps.
All rows of the tip will be knitted in a U-shape, i.e. you knit the stitches on the first needle turn the piece upside down (this point will be called turning-point ("TP") and knit the stitches on the other needle. Then you turn your knitting to the WS and knit back.

Row 1 (WS): k16, pm, k2, TP, k2, pm, k16
Row 2 (RS): sl1, k to m, increase by 2 sts between m and TP, TP, increase by 2 sts between TP and m, k to end
Row 3 (WS): sl1, k all
Repeat rows 2 and 3 until the straight edge is wide enough to fit half way around your feet. Your piece should look similar to the one depicted in photo 1.
Repeat row 3 once more.

(For the slippers in the pictures, I did a total of 9 increase rows.)

Now you basically knit the same backwards, i.e. for each increase row you knitted before, you will now knit a decrease row. Spelled out this means:
Row 5 (WS): sl1, k all
Row 6 (RS): sl1, k to m, decrease by 2 sts between m and TP, TP, decrease by 2 sts between TP and m, k to end
Repeat rows 5 and 6 until there are only 2 sts left between each marker and the TP.
Row 7: sl1, k to TP

Do a three needle BO, keep the last stitch and turn the tip rights sides out, i.e. that the rigde from the three needle BO is on the inside (see photo 2).

Heel

Starting from only leftover stitch, pick up and knit stitches along the rim of the tip - one stitch per garter stitch ridge (see photo 4).

Count the stitches and devide the number by 4 (this number will be called X). In row 1, you will place two markers, one X stitches away from the beginning of the row and another X stitches away from the end of the row. The piece should look similar to the one in photo 4. (I had a total of 43 stitch, 1 leftover, 42 picked up. so I distributed them as follows: 11-21-11 where the 21 stitches made up the sole and both 11 stitches the sides).

Row 1 (inside) : sl1, k X-1 sts, place marker, p to last X sts, place marker, k to end

Row 2 (outside): sl1, kfb, k to last 2 sts bef end, kfb, k1

Row 3 (inside): sl1, k to marker, p to marker, k to end

Repeat rows 2 and 3 three times more.

Row 4 (outside) = sl1, k to end

Row 5 (inside) = Row 3

Then repeat rows 4 and 5 until the length of the slippers are 4 cm short of the total length of your feet.

Now start with the heel decreases:

Row 6 (outside): sl1, k to marker, ssk, k to 2 sts before marker, k2tog, k to end

Row 7 (inside): sl1, k to marker, p to marker, k to end

Repeat rows 6 and 7 four more times.

From now on only one of the side parts (in garter stitch) is worked, the stitches between the markers will be decreased row-by-row and the second garter stitch bit will not be worked until it is joined with the opposite side at the end.

Row 8: sl1, k to 1 bef marker, ssk, replace marker, turn, sl1, k to end

Repeat row 8 until there are only 2 stitches between the two markers.

Then knit the following last ridge: sl1, k to 1 bef marker, remove marker, and do a central double decrease as follow: ssk, slip the last stitch back onto the lefthand needle and slip the next stitch over the former ssk. Leave this stitch on the lefthand needle. Then turn, and k to end.

Distribute the remaining stitches evenly on two needles. Your piece should now look similar to photo 5. Finish with a three-needle bind off on the inside of the slipper (see photo 6).

Turn the heel back right sides out.

Weave in ends.
Make two.