Oma got me some cozy UH fleece a month ago and I've been eager to use it. One thing about the Stranskys, we love us some collegiate gear!
Ikaika has tons of pajamas. Almost too many (IMO). The issue has been that his feet are freezing in the mornings. All the footed jams are one piece jumpsuits, which are a nightmare when it comes to using the potty. Because of this, I prefer to use long sleeve, two piece PJs but it's almost impossible to find them with feet.
I started this project by using an existing pair of pants for the pattern. I turned them inside out and stuffed one leg inside the other then traced them onto my fleece, taking into account seam allowances and elastic squishing.
Because my son wears a massive cloth diaper at night, I added a panel in the back to provide extra room in the tush.
I basically assembled them like regular pants except I added a "shoe" to the bottom. I think the trick here is two-fold: 1) make sure to cut out an arch on the front of the pant legs before you attach the top of the shoe - that way there is room for the volume of the foot and 2) I attached elastic to the back of the leg at about ankle length in order to help keep the foot somewhat snug. This seemed to improve both the fit and mobility.
I might try to use puffy paint on the bottom of the feet to make them somewhat less slippy. Even though he will theoretically only be using these to sleep, there's always the possibility of splitting one's face open on the hardwood floor.
The bummer about pants like these is that there isn't the same growth forgiveness there is with other clothes. You can't roll them up if he's too short, and once he's too long, there's no way to modify them. Looking at them on his body, I think I made them too short (ie. the length is exactly right at the moment) so I hope he - and I - enjoy these while they fit!