Keen to try and use up some thrums with making coasters and weaving two warps at once on the same loom, bit like this:
https://handwovenmagazine.com/uses-for-loom-waste/

However, I had some shorter thrums (9cm) and some longer (15cm), so I made the warps of different widths accordingly.

Learning:
Hemstitching all the way around the coaster did NOT work for me - it was doable, but it was a pain (literally got neck pain) and I didn’t repeat it after the first big coaster. I went with a proper weft and using the thrums as decorative inlays instead - that way, the outer warps were still secured.
Still, this project was all about hemstitching - if not one one warp, then on the other.