First of all, get the children to draw a plan on paper to imagine how their model will look, what film scenes will be represented, what elements they'd like to see...
The model will be divided in two lengthways by the thin plywood board from which the mountains have been cut. The thin board is glued with wood glue, with a support on each side while it dries.
On each side, the children draw in pencil the location of the reliefs: the road for the model on the "Swiss mountains" side, the location of the border post (which must be flat), and for the model on the "Amazon forest" side, the outline of the river's edge.