[Alteration Question] How should I hem stretch men&#039 Sewing Machines Parts and Sales in Los Angeles

Hey Threddit,

I’m a new sewist, and I’m wondering how I should go about hemming a pair of RTW boxer briefs from Target to what would pretty much be men’s boyshort length. Here are the boxer briefs in question (NSFW because underwear model). I bought these to give to my boyfriend as a late birthday/Valentine’s gift, but he prefers to wear really high-hemmed stretch boxers or tighty-whiteys.

These are made out of 95% cotton 5% spandex knit, so I think the negative ease is there. I would like to take the original bias edge on the legs (the raw edges of which are serged together then sewn onto the main trunks) and re-attach them at the level of the low point of the crotch piping.

I know I need to use a stretch stitch and take it slowly, but I’ve never worked with stretch knit before, and I don’t have a walking foot for my machine yet. Is it really as easy as unpicking, cutting the trunk legs off, and re-attaching the bias tape? Or are there other things I should know to do?

Thanks in advance for your help, and happy Valentine’s Day! <3