Here is what I found. Add your resources, ideas, and questions on this topic.
1. Graphic image showing stitching through selvedge loops:
https://www.pinterest.com/pin/67483694392418734/
2. Graphic image of stitching through selvedge, not using the loops
https://www.pinterest.com/pin/199002877261412411/
3. Article about different methods - hidden seam and decorative seams
http://www.eloomanation.com/assembly.php
4. Weavolution group discussion:
http://www.weavolution.com/forum/weaving/sewing-blanket-pieces-together-make-it-larger
5. Book with more details you may own or borrow from your library. Reminder: Even though your library may not have a copy, they can get one from another library. Once I needed info from a library across the Atlantic Ocean. They would not send the book, but they did send photocopies of the 2 pages I needed.
Inventive Weaving On A Little Loom by Syne Mitchell - page 274