Official Luthiers Forum!

Some folks live in a Baltic Birch plywood desert. If you have that problem, but would like to have some for jigs, workboards, etc., I can recommend this outfit:

https://makerstock.com/

I have no connection with them, other than I can report having ordered some BB plywood from them, and what arrived was high quality, flat as flat gets, and packed very well to avoid dings. I ordered four pieces of 24” square, 18mm thick BB plywood. I’m very happy with the cost and quality. There are limitations on sheet size, but if you are not building carcasses or whole workbench tops out of it, you should be able to order what you need.

Just an FYI, in case some folks are frustrated by local choices (as I often am).