I would most likely just stitch & pink the seam allowance - & be sure that the stitch length is very small - on my old machines that's about 18-20 stitches per inch. If seams are straight (like on the outside of the legs), you can press both allowances to one side & topstitch 1/8" from the seam edge.

Here is a link that might be useful: Seam Finishes

I like to make flat fell seams for pj's and boxers, anything that might have some stress to the seams.

Sue

Flannelette frays easily and the threads if the fabric tend to pull at the seam. Flat fell seams are good because you are adding extra strength to the seams. You can also sew a zig zag seam through both seam allowances(held together) and trim the allowances to just past the zigzag. Or you can trim and then overcast. This is what is done on the ones you buy. Both these will add strength to the seam too. I must say the flat fell seam makes the neatest looking seam but sometimes it adds extra bulk on curves.

Thank you all! That is a great link! As I received responses I kept wondering what is a Flat fell seam? As I was reading through the various descriptions I went oh....THAT! I've seen a lot of them, and used a few of them, but could never of told you what they were. I guess I most frequently use the zig zag and overcasting, or the faux french. All I know is that the light to medium weight denim I used for the pants I made is fraying so badly that even the zig zag with triple strength straight probably won't hold it for long. I wasn't sure what to use for these. Since they are really loose (therefore comfy) I'm going to try the Fell flat. So glad I asked and did NOT trim my seam allowances!

Another thing you might bear in mind. Triple sewing seams along the same line will cause your fabric to tear. Try not to sew over a seam more than once. (two stitches on top of each other) It's much better to sew about 1/8 to 1/4" out toward the edge of the seam allowance and use your double sewn seam in the stress areas only. Crotch, underarms, etc.