IF.. I do say "if".. the surface is thick enough, so you can "center-cut" it.. you can use any straight-edge rule.. mark it.. slit it... otherwise the jig mentioned works very well too..
When you're positioning them.. the way I do it is to hold/tape/secure the surface itself to the component attaching it too.. then I simply lightly pencil my positions.. after that is when I start cutting slots to centers..
There is a tool made just for that too.. Its about $15..maybe $20.. maybe less if you can get one used.. I got one years ago.. when theres a bunch of slots(I'm talking 25-35 hinges or so..) multiply that by 2(one slot each side).. that's 50-70+ slots... the GreatPlane slotter just bores through them.. it takes a tad of practice.. as its a thin blade.. and can skew if its hurried.. but still takes about 4hrs or more work and gets it done in 15-20 minutes.. on the other hand if you like to tinker.. and enjoy the time spent doing it by hand.. that's cool too.. can't knock a craftsman.. so.. one other thing..
Be sure to use "thin" CA glue... it doesn't matter whether its odorless or not.. just make sure its thin.. I put about 5-6 drops on one side while flexing the surface.. then same on the other.. just working the surface for about 5 minutes. it doesn't take alot of glue.. but just be careful to not get too much too quick.. and watch for runs.... less is probably best.. and I do a second app of a few drops after about 15minutes..
There's some good instructs in this thread.. so use whatever works for you.. I'm just sharing what/how I do hinges/slots.. Good luck.