Note:

I am using merino woolen yarn 100 - 120 gr. main + 0.5 -1 m of additional yarn of a different color
I’m knitting in 2 threads on circular knitting needles, but you can use 30-40 cm long straight needles
I knit slippers sizes EU 37-38 with needles of 8 mm and EU39-40 with needles of 9-10 mm
You will also need needle with a blunt end - 1 unit