Here’s the pattern - you may decide to tweak it for your own preference.
Use 4 different strands of yarn - 2 of each color - worsted weight,
Size 10 needles
Using 2 strands of first color cast on 30 stitches for ladies, 40 stitches for men
Knit 5 stitches, then start 2nd color and knit 5 stitches. Change color every 5 stitches and carry the strands up the back.
2nd row is the same, but to change colors you have to bring the yarn forward to switch colors, then put it back to knit.
Make sure to cross the yarns over each other at color changes so you don’t have gaps.
Continue in St stitch until you have 25 ridges (ladies) or 32 ridges (men size 10 foot)
Next row dec 1 stitch in each stripe .Knit back
Next 2 rows dec in each stripe again. (3 stitches in each stripe now)
Gather all these toe stitches onto a double strand of the yarn and tie it off. Stitch up the top of the foot and the heel.
It is sort of a pattern I figured out from an existing slipper. I can’t promise professional results on sizing and etc. Just try them for yourself. I have also knit them up with 2 single strands of that Lion Jiffy thick and quick. The sizing seems to be the same. It’s a little easier to manage 2 strands than 4.
Put all the balls of yarn in ziplock bags and that avoids most tangles.