How is 5.x kernel backported when we don't have gcc11 in Stable?

[Simon John <debian@the-jedi.co.uk>]

I was trying to backport the 5.18 kernel as an exercise, but I noticed 
that it requires gcc11 to compile it and Bullseye only has gcc10.

So how is the 5.18 kernel backported - I assume its not simply compiled 
on a Testing box, as that wouldn't be a backport (might as well just 
install the testing package!)

The whole backports process seems poorly documented - with references to 
various options e.g. pbuilder, cowbuilder, sbuild, deboostrap, schroot, 
all the way down to a simple dpkg-buildpackage/debuild....

Is there a preferred/official method?

Thanks.

--
Simon John