Single sock
Sit down and grab the sock a few times with your toes. A towel or tissue would also do.
Start by grabbing the sock only a few times and then gradually increase over the coming weeks. This is probably new to your foot muscles and you do not want to tire them.
With any “training program”, we tend to want to do too much at the beginning and then we do not stick long to the practice. So, better do the opposite: Start easy and keep having fun with it.
Do not forget the other foot.