Only gaiden is For Old Times Sake.
You sneak by not ever getting into combat with them. If you just check the global ranges before placing you should be able to figure it out. Think of it like a puzzle where you need to get the enemy phase units to move in ways that leave squares open for you to use.
The map has no RNG if you don’t enter combat, so it’s just a matter of testing possible solutions.
If you want specific help PM me and I’ll work with you on getting a solution for normal/hard (I have to double check my notes for lunatic, IDR if I had strats for skylar without boots)