How to use encryption key(on flash drive) instead of pass phrase

[Frozentime345]

I was trying to follow the custom install guide to do this but keep
failing at "setting up installation environment". Preferably I would
want to use just the key and not have any pass phrase.

I learned that you can change the encryption key in dm-crypt so maybe
the easier method is to install and then add the encryption key? I can
try experimenting myself with some clues if this method makes sense.

Also once I get all this working, how does one start up the system using
this method? Is there a way to escape to shell and use cryptsetup?

Finally, I'm using this command to generate the key :
sudo dd if=/dev/random of=filename bs=1 count=4096

Is this okay?