This is the best I remember from my Grandma making house slippers for friends and family back in the 70s. I have tweaked it a little to keep the symmetry and shape in tact. Depending on weight of yarn or size of hook you can make a child’s size, an adult ladies small (5-6), medium (7-8) or large (9-10 which may also work for a men’s medium).
These instructions with a worsted weight yarn #4 and a 5.0mm hook will make a ladies medium.

I’m working on modifying it for baby booties and toddler slippers.

This pattern is worked in the round for toe, instep and cuff. The heel portion will be back and forth in rows.

You can alternate colors as much as you wish or in whatever stripe patterns you want. I have not tried it with ombre yarn, but I think it would be amazing to use that and see how the color changes as you work from the toe going back to the heel.