Here’s a quick video giving you a visual on a simple sewing trick – how to get the seam of a fabric tube to be perfectly at the edge when you press it flat. This comes in handy for making things like spaghetti straps or belts.
The process is simple. Turn your tube of fabric right side out and lay it down on your ironing board so that the seam is straight. Pinch the seam in your hand and work your way down the tube, rolling the seam back and forth between your fingers, while you press the tube flat. I think this makes more sense if you watch the video!