I didn't really use one but I used this as a general guideline.
I however, did not use the heel of the sock to make the monster be able to sit. I used the heel of the sock to make the fun mouth on mine. I found my crazy socks at Freddys on clearance for about 2 bucks a piece. If they are socks that go to the knee, I was able to get 1 monster per sock. If they were just above the ankle socks, I had to use the other sock for the arms.
To start, turn them inside out, flatten them with the heel up. Draw a general body pattern on the sock, using the link above for guidance (I used a sharpie marker for light colored socks and a white makeup pencil for black or dark socks). I used a sewing machine on low tension to sew the body and the arms. Be sure to leave a hole in the crotch so you can stuff him with fluff. Turn it right side out. Stuff him. Sew up the crotch and sew on the stuffed arms using a needle and thread. Also, tuck the heel in and sew it in place to create the monster mouth. Buttons and felt for the face and details. And walaaaaaaaah! You have a naughty little sock monster.
Oh yeah, don't forget to include a cute tag that says: This sock monster was made for you with love, by Natalie....and then give each of them a name (this was the fun part, we went with nursing home names) and some hilariously quirky characteristics and you are good to go!
Super duper economical gift. I was also able to find some fun socks at the Dollar stores in town. When I first started sewing, it was just kind of a trial and error experiment. I even used a couple for experimenting. But it got easier after a time. They do take over 2 hours to do one. So it is going to take some time if you do more than one. So plan ahead.
But do be careful, it doesn't take long once they are complete for their naughtiness to erupt.
Don't say I didn't warn you.