It seems obvious that all you have to do is "just" align the pattern, and sewn down the fabric length in the exact spot where the pattern motifs match up, right? However, accomplishing that quickly AND accurately is not easy.
Years ago I learned a technique from a professional sewer, as I watched her reel off width after width and join them speedily and perfectly without pinning. It takes a lot of repetition to become proficient, so I take every opportunity to practice.
The other day I faced a stack of orders all requiring widths to be joined, so I decided to cut and join all of them in one afternoon, to keep in the swing of the process.
I started with the easiest, a cotton gemetric print.
It only needs one photo to illustrate this technique. One width is laid right sides together atop another width. The top width is folded back 1/4" and laid down along the underneath fabric, aligning the pattern. Then before sewing the fold is nudged over to the right about 1/8". The stitch line is about 1/16" from the folded edge.
This is done by eye, perhaps pinning 5" ahead. Some pattern details, like the center of the V below, make good "marks" to look out for, as well as the selvedge markings.
Yeah, this can be done!
Afterward you trim the selvedges, and press from the right side.