build a simple 3/4" plywood box
The freezer has feet in the corners, so any weight transfer will be where a box that's the same size made of 3/4" will have the greatest strength... in the corners!
You plan seems way overkill for a 100 lb. total freezer. If you plan to move around some 2" or 3" casters on the bottom would be nice and raise it off the floor for greater longevity. Otherwise, make some 2" X 2"rails to raise it up. Leave the face open for storage. I'm thinking a 10" or 12" high box... what do you need?
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)