Flannel is so cozy and I like wearing PJs beyond t-shirt and gym shorts to sleep. This is really just a personal preference.
During my first major haul of when I purchased all of my start-up stuff for sewing I picked up various flannel from the remnants bin at Joann's. I had not had anything particular in mind in terms of what I was going to do with it. All I knew is that I like flannel and I liked the patterns.... and it was cheap.
I wanted to try my hand at making apparel without a pre-designed printable pattern so I went with something simple like these shorts.
Step 1: Fold flannel in half and then trace the shorts twice giving a lot of space for hemming, adjustments, and the fold-over waist band.
Step 2: With two of the pieces, right sides of fabric touching, sew along the inseam of each pair of fabric. One pair will become the front of the shorts, and the other pair will become the back.
Step 3: with the fabric from step 2 complete, open it up and with the right fabric sides of the completed front of the shorts touching the right sides of the back of the shorts so the wrong sides of the fabric are facing you, sew down the sides of the shorts, and sew the inseam. I didn't take a photo of that, but hopefully based on how shorts work and the holes your legs have to go through you can figure it out.
Step 4: Cut elastic to fit your waist, but smaller. Stretch out the elastic as you pull it around yourself to get a feel for how long it needs to be, and add a little extra for good measure.
Step 5: Sew the top of the shorts in, with the wrong sides of fabric touching wrong sides of fabric, to a width that is a bit wider than the width of the elastic that will be used. Sew along the bottom edge of this around the shorts with a few inches of a gap so you can insert the elastic waistband. Use a large safety pin on one end of the elastic waistband and with the safety pin on the elastic, push that through one end of the gap and then push it through the entirety of the waist, making sure you don't accidentally lose the other end of the elastic... you could safety pin that to the gap if you want. Sew the elastic together where it is a most comfortable fit for you (so you should try the shorts on). Sew the gap closed.
Step 6: With pinking shears, trim the edges of all the exposed frayed edges that you will be finishing up. With zig-zag stitching, finish up the edges.
Step 7: I "roll" hemmed the bottom of the shorts. Rolled hem foots do exist, but the "roll" was large enough with this that I don't think I would have benefited greatly from one. Hem along the top of the roll, away from the edge.
Ta daaa, new sleep shorts. Very comfortable.
Now it's time to sleep. Goodnight!