When you line your cage, cut a square out of each corner, then fold the sides up (the width of the square removed) so the edges meet & contain stuff better. 'Cause
you KNOW snakes are gonna leave stuff so it overflows the edge of the liner otherwise, if it's just cut to fit.

It's been a long time back, but I've used the corrugated stuff from Uline (it's like corrugated cardboard that's open face on one side), works pretty well, though I never
kept anything like a big burm on it, lol. (maybe you should get some Pampers?)