Here's an interesting forum and thread I came across the other day. I was searching for traditional uses for birch. I'd seen an old film about a Finn fitting a new birch handle to his axe and wondered if anyone still appreciated birch handles. This thread is very instructive in carving, fitting and fine tuning new handles.
https://trapperman.com/forum/ubbthreads.php/topics/5380602/all/Making_axe_handles_and_birch_b
https://trapperman.com/forum/ubbthreads.php/topics/5380602/all/Making_axe_handles_and_birch_b