To prevent the mob from simply jumping out once the pistons fire, you need a ceiling.
Ensure the mob is fully contained. If a part of the mob's hitbox is clipping through the piston, the game might not register it as "trapped."
Whether you are an achievement hunter or a Bedrock Edition veteran, this verified guide will walk you through the simplest, most resource-efficient way to tick this one off your list. The Goal: What is a Piston Trap? lovely craft piston trap achievement guide verified
(Regular Pistons also work for most versions, but Sticky is "verified" for consistency). 1 Pressure Plate (Stone or Wood works best). 4 Solid Blocks (Cobblestone, Dirt, or Wood).
Now comes the "Lovely" part. You need a mob to step on the plate. To prevent the mob from simply jumping out
Place a temporary block two blocks above the pressure plate. Attach a solid block to the bottom of that temporary block. Break the temporary block.
To trigger the achievement, you must construct a mechanism where a mob (like a Pig, Zombie, or Creeper) steps on a pressure plate, causing pistons to extend and block their path, effectively trapping them in a 1x1 space. Required Materials The Goal: What is a Piston Trap
The achievement is a great introduction to basic Redstone logic. By using the upward-piston method, you create a fail-proof cage that is guaranteed to satisfy the game's requirements.
If you've built the trap and captured a mob but the notification hasn't appeared, check these common issues: