As a learning exercise I designed and printed a new insert for my Delta miter saw. I designed it in Autodesk Fusion 360. It was longer than 250mm so I had to rotate it so it would just barely fit diagonally on the bed of my Makergear M2 printer. The darker one is the original that came with the saw - I’ll put that one back in when I do non 90 degree cuts so the new one will stay precise.
Did you print the slot or just let the saw cut it?
I let the saw cut it - typical procedure when setting up a zero clearance insert.