How to turn this:
Step one: find a pair of knee high socks. I get most of mine on ebay but I've also gotten them at goodwill and Walmart
Step two: Cut the foot off the sock:
You now have 2 pieces:
Step three: trim up the foot part (the arch of the sock) by cutting off the heal and toe:
Also make sure that the arch part is squared up as this will make it easier for you to sew. The best way to do this is to fold the tube of sock top to bottom and side to side to make sure there aren't any pieces longer then others. Also make sure both tubes from each sock are the same size!
Step 4: Trim about a 3/4 of an inch off of the arch of the sock. This part will be your cuff and if not trimmed smaller will make ruffle rather then a cuff.
These are the only two pieces you need to make your leggies all other parts can be thrown away:
Step 5: take your 4 parts (for both socks) to the sewing machine. using the arch parts of the sock, put right sides together so that you are looking at what was once the inside of the sock. Make sure that you have the tube as it once was, as if to put it on your foot. Line up your raw edges. Sew raw edges 1/4 of an inche from edge. I use a zig zag sticth to give it more stretch and because it's more forgiving. If you don't have a sewing machine you could whip stitch the seams.
Step 6: (forgive me I'm having a hard time putting this part into words) Turn the tube you just created so that the top and bottom openings match up. this makes your tube half the height it was and your seams are now inside the cuff you have created. (see pictures, it's worth at least 30 more words)
Step 7: Line up your cuff and the top part of the sock so that the nice folded edge of the cuff points towards the raw edge of the sock (see picture) put your hand inside of the cuff and grab the raw edge of the top part of the sock and put the cuff on the sock (upside down so that the nice edge of the cuff points towards the top of the sock.
Step 8: you should now have 3 raw edges lined up. 2 from the cuff and 1 from the sock. Make sure that all 3 edges line up nicely. you could pin this if you need to. If hand sewing, whip stitch these 3 layers together. If machine sewing, you are going to put these 3 layers under your foot leaving a 1/4 inch seam allowance. Be very careful that you don't catch the other parts of the cuff as you stitch. Stretch the cuff as you sew but don't stretch the sock. make sure your needle is down each time you adjust the sock and cuff. I sew a little bit and put my needle down, stretch the cuff and realine everything every so often. Make sure you back stitch to lock your stitches in or when you put the leggy on your baby, it will come unsewn. When you are done, pull the cuff back down so it's now pointing down and check your seam to make sure you caught the sock all the way around. the sock likes to pop out of your hand and because you are working with 3 layers it's often hard to see.
As you can see, it's not a perfect science and even though I started out with two pairs of socks that are the same, I ended up with one set of leggies shorter then the other.
In my head it's simple but it was hard to put it in words. Feel free to ask questions and I'll try to answer them!!