The 12" masking the OP and others are referencing is something called vinyl transfer paper. It’s not vinyl, it’s a paper based product commonly used by people making vinyl decals & lettering that allows the vinyl to be adhered to a surface like a glass door & the paper masking removed. It’s a low to medium tack adhesive and removes easily. It’s commonly found in 6 or 12 inch by 100 yard rolls.
It should unroll fairly easily and apply to something like plywood without a lot of fuss like tearing and sticking to other stuff. It gains its adhesion by using a roller (printer’s brayer) or plastic card to squeegee it onto the material surface. It needs the pressure to activate the adhesion to be more than minimal tack
Masking tape like that from the big box stores found in 4" rolls (like painters tape) is a higher tack adhesive - even the blue or green medium tack varieties (run far away from the light cream colored masking tape - that’s a high tack).
The problem with narrow rolls like 4" is you’re going to either have the slightest and even imperceptible gap between rows or overlaps between rows. The gaps will cause more power to be delivered resulting in a very thin line of darker engraving. Overlaps will result in less power getting through the overlap line and thus a line of lighter engraving or possibly a mis-cut.
Transfer paper is the thing to use.
BTW, I only mask the top surface. For the bottom I use either newsprint or white copy paper on the honeycomb bed as a sacrificial layer. It’s quicker than masking and just as effective in preventing flashback.