Best way to mount wood lettering on a wall

We’re using 3/4” plywood and they’re cut in a fairly thin font. Some of the letters are connected in cursive but others are stand alone. We’re wanting it to be flush and not any noticeable screws or mounting hardware.

Had someone recommend construction adhesive to bond it to the wall. Any recommendations? I was thinking maybe a mix of that adhesive and a nail gun to hold the letters in place while the adhesive sets them touch up paint the nails. They’re pretty light weight considering the size of them.