I love mob traps! My favorite had been Society's setup, but trapdoors can't be placed in water anymore
What I've been doing so far, on Android, on the surface (underground needs testing) uses the basic design of Society's trap with wide stairs, water and acid. My pit is two deep, acid in the bottom and water flowing in the top. My center is 3 wide, ( 1 wide for safe standing) with a 5 wide roof extending over the pits, a ladder in the middle. Instead of blocking mobs with the trapdoor, I place a solid block to stop water and mobs while I remove an inner wall to collect items, then remove the block from the relative safety back inside. It's been working pretty well!
Warning, poor diagram below! O - open air, # - solid block, A - acid, @ - ladder
Open for business!
OO#####OO
OOO#@#OOO
##O#@#O##
##A#@#A##
####@####
Closed for collection
OO#####OO
OO##@##OO
##OO@OO##
##A#@#A##
####@####