You will need a remnant of 4-way stretch fabric and matching thread. Polyester/spandex blend makes a nice sleepy hat. Brushed rayon blend is cozy for outdoor winter activities. I think this would also work if you were careful to horizontally orient the stretch of a 2-way fleece. But this is South Florida and that's theoretical.
Step 1: Cut & Pin
A 5 quart bowl was just right for cutting a hemispheric pattern. Then pin the cut edges.
Step 2: The Faux Felled Seam
The 2nd row of stitches takes a little more explanation. With the outside still out, I put the free arm inside the cap. Both sides of the seam allowance are folded together flat. Then the 2nd row zigzags across the seam to capture the fabric edges.
The end of the seam folds to a point and everything is neat.
Step 3: Hemming
Step 4: Done
Yes they do make great gifts. Cheers from Sarasota.