The Node 304’s side and top panels are of a single-piece.
As for the interior, it’s extremely compact. See the white panels? They are the holding brackets for storage.
The storage holder hovers just above the PSU, notice that black frame? That’s where you mount the PSU.
Mount your drives whichever way you see fit. The holding brackets are removable.
The holding brackets are probably one of the beautiful aspects of the casing, it’s just too bad it’s hidden.