I get the 45 degree bank by looking at the screws of my instruments. Since the screws are placed in the "corners" of the non-existent square hole, the diagonals are 45 degrees to vertical/horizontal.

When I bank over, I check that a diagonal parallels the horizon (I'm a flat-lander) and the other is perpendicular. Easy-peasy!

Now, if I can just stabilise my speed and the angle, I might improve my thermalling. I keep working on that