On canvas, denim and other tightly woven fabrics, if you don't have an overlock seam on your sewing machine, you can simply bind the raw edge by zig-zagging the edge so that one side of the seam (zigs or zags, up to you) is just outside the fabric (less than 1/32 inch). If the fabric is very coarse, do that twice with different seam widths. The lighter your fabric, the narrower you want your zigzags, so as not to curl the edge.

Or you could do a rolled seam as seen on some commercial jeans: Place fabrics together with both pieces right side up, sligtly overlapping. Sew a straight line down the middle of the overlap. Roll the seam to hide raw edges and top stitch on both sides (or with a twin needle). This is has to be done before you pleat the kilt, though, and you need a very sturdy sewing machine. Kind of cheating a flat felled seam. Thanks to Barb T. for teaching me the "true" flat felled seam.