I made these for my friend, for her birthday.
I was scared she wouldn't like them, but when she unwrapped them she said "I love these things!"
I knitted them with size nine needles. I used a soft and fuzzy yarn that's a little bit thicker.
Here's what I did:
I knitted the toe in two separate pieces, then sewed them together.
Since the yarn and the needles were big, I only had to cast on 12. Just measure your foot from side to side right under your toes(I guess that would be the widest part of your foot), then cast on that many stitches(a little extra is okay, for the sides. But there doesn't have to be extra, since the yarn will stretch). A lot of the decreasing is just decreasing where it looks right. Most of the decreasing will be done on the side of your foot where the little toes are. By your big toe, there may be one or two.
After sewing the sides together, I picked up the stitches and knitted the bottom and sides of the slipper. If you knit it wide enough, the sides will just curl up and you don't have to do anything extra difficult
The heel is a little hard to explain. I safety pinned 3 stitched on each side so the stitches wouldn't fall out (you will come back to these later) the rest of the row is what you knit for now. You decrease the first two stitches and the last two stitches. Repeat once and bind off.
Then go back to the stitches that were safety pinned and knit until it is long enough to wrap around the heel. Then sew them together, then to the heel.
If the sides aren't long enough, you may have to crochet around in the main color.
After you're done crocheting around in the main color, use a different color(or the same:)) to crochet around once. I did single crochet around most of it and double crochet at the heel.
I also suggest making a strap, so they can look like mary janes