I did build an inexpensive platform with plastic boxes instead of drawers from OSB wood boards (hope that translates into English …) last night:
Measures:
Thickness of all boards 0,18 cm
Top board:
Width 106 cm
Depth 90 cm
Bottom board:
Width 88 cm
Depth 82 cm (should have been 84 cm but I mis-measured and cut it short – still works as intended)
Left, middle and right perpendicular boards:
Length: 82 (should have been 84) to 90 cm
Height: 14 cm
All glued together with wood glue and screwed with 7 cm long screws.
The boxes have following measures:
2 boxes of 60 x 40 x 12 cm
2 boxes of 30 x 40 x 12 cm
The wood has cost less than 30 EUR, plus some would glue and some screws and some 35 EUR for the plastic boxes.
Here are some pictures.
2 of these boards were used (Length 205 cm, Width 62,5 cm):
View attachment 7817213
Top board in the background, bottom board on the floor, perpendicular boards just put on top of it:
Top board and bottom board are out of 2 pieces each.
View attachment 7817214
Bottom board glued and screwed on to the outer perpendicular boards:
View attachment 7817215
Top board glued and screwed on all 3 perpendicular boards, boxes inside:
View attachment 7817216
internal platform in Grenadier, backseats put flat:
View attachment 7817217
internal platform in Grenadier, backseats upright:
View attachment 7817218