The shirt, $3 from Goodwill.
Pattern pieces made from existing pj bottoms, traced front and back.
Pieces cut for the front and back. I usually use the side seam of the shirt for shorts, but these are a bit too long for that, so I had to sew up the sides on these.
All done except the waist. I made sure to iron my seams all flat. Dana, from dana-made-it.com gave this great tip! They look so professional. I love these. They are bit big in the waist for my son, but he is growing so fast, no doubt they will fit him before winter time is over!