I want to build my flash cart... but...

I want to build my own genesis flash cart because I've seen some people here, specially Arakon talking about their own flash carts. I read things like bootleg cartdriges, rewiring some lines, using four 8 Megabit eeproms, etc... but, could someone explain it a little detailed so everybody could understand it?

What things I need (which cartdriges I could use to add slots for eeproms and don't have to rewire a lot, etc), which steps should I do, etc?

Help really apreciated!