This is similar to this question, but the solution there was to choose the disks using "device=/dev/sda1,/dev/sdb1", which is not as robust as using UUIDs. I'm sure it can be done, but I can't find any examples/documentation using UUIDs for the individual disks.
The closest example I could find is here, but that's using "by-id" device=/dev/disk/by-id/ata-HGST_HDS724040ALE640_PK1334PBG3GYHS
instead of UUID which I'd prefer.
Using that as a template, I tried UUID=3d12bc7b-61b1-4dea-b78b-ef9a44a6b698 /media/btr0 btrfs device=/dev/disk/by-uuid/6dc5624c-2d54-4726-b2fa-a7a988d337a4,device=/dev/disk/by-uuid/b57f2240-fa2e-4516-9049-603d2c5029b5 0 0
but it didn't work. Any ideas?