This is a mob farm style from Etho that I used to make this farm. Notice that inside the spawning pads have slab in the middle of them to prevent spider spawns (because they will clog it.) I don't use mapmaking tools for ANY of my maps so it puts in the fun of building it. But this farm is 3 layers, 12 pads each layer with a collection zone below. This farm is simple to make, but consumes a lot of blocks from your supply. The best block to use would be snow blocks because you can simply farm snow from snow golems. I have made one on a survival server. Only 1 layer took 9 stacks of snow so I do recommend getting a snow golem to farm snow from to make this farm. Once it is done it is SO worth it. Especially with the 1.7 update with the natural witch spawns allowing you to obtain potion ingredients and healing potions. NOTE: You can make this as many layers as you want. But 2 - 4 is recommended to keep it spawning because the layers are within spawning range. That's about it. Enjoy building your own and don't forget to DIAMOND if you want to :) P.S: I WILL get downloads enabled too and I will update the uploads i make before I get the downloads up. NOW ENJOY :)