For DIY there is thinner material available for very cheap. Order a few sheets at a time and they come shipped flat instead of rolled. I do not recommend a knife and especially not a drill for DIY. For long cuts, use a good set of scissors. For holes and other cuts use a punch set and high quality wood chisel set. Line it up, use a decent backing (piece of metal or plastic cutting board) and whack with a hammer and the cut is nice and neat. I've made a few protectors that look like they were cut by laser.

https://smile.amazon.com/gp/product/B00B1U1X4A/ref=ppx_yo_dt_b_search_asin_title

https://smile.amazon.com/gp/product/B000Q7AVL0/ref=ppx_yo_dt_b_search_asin_title

https://smile.amazon.com/gp/product/B07Q2L6W5W/ref=ppx_yo_dt_b_search_asin_title

I basically only use them on old games with cupped inserts. This is the magic fix for cupped inserts!