Divide the table into 24" (about 60cm) square areas. Roll a D3 for each area, this is how many pieces of terrain will be placed in that area. Roll 2D6 on a random terrain generator (see below) for each piece of terrain in each area and position that piece of terrain anywhere within the area. If you want, you may place terrain pieces on top of each other to create, for example, a hill with a wood on top of it.
Setting Up Terrain – Method 4
Source: Core Rulebook 3E, p. 124
Divides the table into 24 inch squares and rolls a D3 and 2D6 per square against a random terrain generator to fill each one.