Frame - I measured the length of playfield and then cut the sides and top of 2" X 8" to length with 45 Degree Miters (as shown in picture). One was mitered on 1" side and other on 2" to give the frame depth and coverage for the playfield and inserting lights.
I glued the two frames together with wood glue and also screwed corner brackets onto corner. I used large clamps and painters tape to hold the frame together.
After the glue dried, I screwed in corner brackets (likely over kill) and screwed playfield to frame with existing holes (I did want to make the process reversible and not cause damage to playfield).
Populated the playfield with plastics left over from a previous restoration. Covered large holes with photo gel paper to match colors on playfield.
Strung the Christmas lights behind the playfield into the GI holes under the plastics and pop bumpers, to have an always on incandescent feel.
Put the LEDs in a random pattern underneath on the fiberboard. These jump and make it look like playfield is in attract mode and provide a blinking effect.
Screwed the fiberboard to back of frame and mounted onto the wall.