If you love to sew with knits and do not own a serger, you can still easily create a slightly stretchy seam by using a crooked straight stitch. Any sewing machine with a zig-zag stitch capability can create this kind of seam—it’s easy peasy!
Set your stitch width between .75 and 1.0, and the stitch length between 2.5 and 3.0 Experiment with a few different settings on your fabric to see what you like best. On a thicker knit you might even need to increase your stitch length to 3.5.
By adding a slight amount of width to a regular straight stitch you create just enough stretch to help prevent your knit seams from popping during wear. Try it!