Cut levels under hex grid hill shapes
PDF demonstrates that in order to get to 1 inch high, you don't have to make a hill look like hexes UNDER the top layer; just concentrate on making the top layer and radiate outwards successive layers of foamcore until you get to one inch high, or higher. But remember, the higher you go the more the layers radiate outward. Glue the layers with wood glue and weigh down during drying (4 hours for large hills) with power tools. Make sure when putting on the layers they don't slip during the drying process so use good weights and FLAT surface. If the top layer of hex shape is 1/4 inch, then only three 1/4 inch foamcore layers will be needed to get to a total of one inch.
Remember, all your terrain must be height-wise accordingly; for 1/72 figures (other than WW2 and NOVA) we do not have trees or buildings taller than 1.5 inches. As trees wont sit on the edge of a staggered hill terrain, stick them in place with StickyTac or use pins; to cover the holes when the pins are removed again, just repaint the hills.
Note that getting colored foamcore is not likely so white will have to be painted; Krylon is recommended so spray outside, without your glasses on, and with a smock and upwind from the object being painted!
https://1drv.ms/b/s!ApNSn4lPCCzogcVN4zTVdpilCS5-kw?e=8vjCec