Minecraft wiki entry for Starting_in_the_Nether, associated text: Build a Blaze spawner farm without redstone
Build in a diamond shape with 1 block of air above, 4 blocks on each side, and 9 blocks below the spawner, then (at the bottom) funnel in by one block each row down until you get to a one block hole. Drop the hole down two or three blocks and then leave a one block gap at the bottom so you can kill them and collect the blaze rods. This gives you blaze rods (craft blaze powder to make an ender chest with!).
Blaze Farm With ZERO REDSTONE by Prowl8413
Build crash bars across walk ways
Put blocks across the hall way the third block up to protect you from Wither Skeletons.
Take the chest too.
Break the chest. Sure you have unlimited wood, but at least you'll know which areas you've already been in.
Farm spawning locations
On Bedrock, nether fortresses have specific spawning locations spread throughout the fortress, probably corresponding to the individual structural components.
silentwisperer - Using glass panes or fences
FoxyNoTail - Using command blocks or guessing based on structure