Just spray down the area you're working on with soap and water or something slick like that and stick em on, use a cc to squeegee out the water once you've aligned them and done.
I had some of these on my old 2020 F150 in silver. Hard plastic letters that fill the indentation. Can seem to find the same thing for the newer F150's in the smaller size. Really want some red ones to match the light bar.