Mike will probably answer too, but here's my view:
Owner RWE permissions, Group RE and World RE is standard, I think.
The thing is that it should be not about /home/spot but about the folder inside the Brave-portable that contains a "spot" directory (after running LAUNCH).
If you run the LAUNCH script (that's how should run the Brave-Portable) from the portable Brave folder, there should be created PROFILE/spot/Brave-Browser inside the Brave-portable dir.
Is it created for you ?
If it's there, check the permissions of PROFILE/spot/ by opening terminal IN PROFILE and run ls -l and it should be like this:
# ls -l
drwxr-xr-x 3 spot spot 4096 may 5 20:04 spot
drwxr-xr-x = owner (should be spot), has RWE permissions, Group RE and World E . (or World has RE, that's okay too).