Now the relevant presents have been given, I can post the pictures!
Not my pattern; the pattern can be found here.
I used a bulkier yarn and turned on each round; this gives a nice textured feel, so they are reasonably no-slip, as slipper-socks go!
I had to change the numbers of shells and rows a fair bit due to the yarn size difference, but, as this is a toe-up pattern, checking fit as you go is fairly easy.
And a matching set: