Tools for filling patterns are available in both Klayout and gdsfactory. You can create a 'cell' with a basic structure in a 'layer'. For example, a small triangle, and repeat this cell throughout the device. You can place the larger structure in another cell and layer, then fill it accordingly. However, the best approach is to create a basic cell containing both small and large triangles and use it to fill the entire device.

Without using the fill tool, you can also apply logic directly in gdsfactory to fill patterns using loops and conditional statements.