I was watching some vids on how to build simple blaze farms. My past blaze grinders have not worked very well, but the "simple" ones I see on YouTube still involve a lot of redstone, and in my new world I haven't found a lot of redstone yet. So I tried out this design and it works FANTASTIC!
I built a 9 x 9 x 5 high cobblestone room around the blaze spawner. Those are the inside dimensions. Outside, the room is 11 x 11.
Beneath the room is a funnel of glass. Each step of the funnel is 2 blocks high so the blazes can't climb out once they fall down one stage.
Under the bottom of the funnel is a bottom slab. That prevents the blazes from ever seeing you or being able to shoot fireballs at you.
You stand at the bottom and whack their feet off. In something like 15 minutes or so I got to level 35 and collected 1-1/2 stacks of blaze rods. All without redstone of any kind.
Here's how it looks:
One word of warning. You WILL die a lot during the building of this farm! I think I died about 10 or 12 times. I started out by encasing the spawner area, 9 x 9 x 3 in netherrack. That stopped the blazes from spawning so I could build the room and the funnel. But then I had to hollow out all the netherrack to activate the spawner. That's when I got killed a lot. I just went in with nothing but a cheap iron pick and chipped away netherrack until I died. Then I ran back in with another cheap iron pick and did it again. And again. And again. ... But in the end, it was worth it, because I got so much XP so fast it didn't matter that I died so many times.
On Edit: Make sure your nether portal is far enough away from the blaze spawner so that when you port in after dying the MOBs all despawn so you can run into the room while it is still empty of blazes and chip away until they start spawning and kill you.
1