Filter Placement Ruud UBHA

Question

Morning;
Purchased a condominium in Florida with a Ruud UBHA unit installed.
Owner had store bought filter duct taped to bottom of unit.
There does not appear to be a 'tray' system to slide filter in and out. I do see a slotted opportunity but appears that could only take the free form filter as there is not entry in from the side, only by forcing one in from the bottom.
Is there a missing tray that attaches to the bottom of the unit to house the filter?
Your help is greatly appreciated and your time well respected.
Thanks,
Brad