Go to youtube and search "shoot film like a boss", which is a generally good channel.
This photographer likes larger square prints and uses a matboard cut with the correct size window, plus a smidgen or out sized border.
He makes his prints using these taped down to his table, using angle brackets, to weight the board flat upon the paper.
After this, he has a board to mask the entire print, that uses the slightly over cut window to allow a thin line black border all the way around the print edges.
Its just that easy and if you are no able to cut windows on your own, just buy some heavy rag board at your most trusted art store (or take what you have) and pay to have windows cut to the sizes you want to use.
I suggest you have two sets cut each time, so there is always a spare when you spill your Absinthe, in the wrong direction.
I also want to suggest using a thicker sheet of iron/steel cut oversize to the outer mat, which would allow you to use middle of the road strength, ceramic magnets, like Harbor Freight sells in pairs to hold down the board and print, then masks.
The reason for this is, you can mount the working boards to their own iron base, and when no in use, file them away in a multi slotted wall, open face cabinet, so the are protected from becoming ill adjusted when stored flat or left lying about.
I built one of these for my last darkroom before moving here and for ease of operation, I took sheet cardboard, such as contractors will place over finished floors, cut it and bent two sides down on the top and bottom, into a 1.5 -2in. straight fold, which I simply stapled into a vertical positioned, starting at the far side of the wooden cabinet which, I could then slide each easel into when no at uses, including my good metal easels.
Depending on the largest (thickest) size used, you can easily keep a dozen easels ready to go, a simply reach away from or by your printing station.
IMO.
