I’ve woven a header from bundles of scrap yarn. (That’s the green and white mess at the bottom of the photo.) This spreads out the warp. Once the warp is relatively parallel, I start weaving with a contrasting yarn to check for threading errors. Once I’m satisfied with that, I weave in lines to guide any stitching, cutting, and fringing I’ll need to do later. Then, finally, I start to weave the fabric itself. This piece has a complex warping/threading process, but the weaving is a simple twill treadling.