I designed a piston door, that opens when you place a redstone torch against a specific block. This block will destroy the redstone torch and the door will open at exactly that block (block is part of the piston door).

Download Litematic Files:
1st design (trigger on one side)
► click
2nd design (trigger on both sides)
► click

Showcase and block-by-block tutorial: YouTube
Note: Map built in 1.17.1. You can change all of the deepslate blocks to any other building block.