Hey there,
First off; I really hope you aren't planning on passing these blotters off as something they're not. Do not sell someone blotter saying it's LSD when in fact the chemical on the blotter is a DOx for example. That's just really bad on so many levels. It's a complete lack of honesty and the effects of LSD are quite different and don't last nearly as long as DOx's. It's not fair to someone expecting an LSD trip and then getting something quite different (which could end up badly).
If you are just laying blotters for a convenient dosing method then by all means that's okay, but there's a chance someone will think it's LSD, or somewhere down the line it will be called LSD when in fact it is not.
Generally only chemicals that are active in small dosages (2mg or less) will fit on a blotter. Generally this relates to the DOx class of chemicals. They are the most common LSD blotter adulterant.
The principle of laying blotter is simple but the actual thing is kind of tricky. You have to know exactly how much liquid a square of blotter absorbs. How you figure that out I don't know for sure. From that number you calculate out how strong to make the liquid solution. Honestly, if you don't know how to do those kinds of calculations you probably shouldn't be doing this kind of thing. It can be dangerous if you don't know what you're doing.
After you have the liquid solution made up, submerge a sheet of botter paper in the glass pan holding the solution, let it soak, remove the paper, let excess drip off, then hang the paper so it can dry off, leaving the chemical embedded in the paper.