No, they're not usually made like that, drops at a time. They can be, yes, if you can be arsed dropping onto each square with a pipette, but more commonly you'd soak the entire sheet when you lay blotters on any kinda scale, typically using very slightly more solution than the blotter will actually be able to absorb to make sure they're all evenly wet then just leaving it to dry, using a carrier like water or ethanol that will evaporate off with enough of the substance in question dissolved into a given volume of solution to give a certain dose per blotter. You'll get some variation in the exact dose of each individual square across the whole of the sheet but one half of a single square is gonna be much like the other half. No problem cutting them at all and if you half it exactly you'll get near as dammit as makes no difference a half dose. No worries.