In preparation for this project I bought a few sprues of Renedra plastic gabions. Primed grey then washed and painted in a variety of woody colours.
I stuck a bunch into the foam with a hot glue gun; concentrating on the gun emplacements first before throwing a few around the other trenches.
Next up I built a shooting step using a collection of (I think) bamboo that was cut-offs from a blind we bought:
The saps had engineering pavises dug into the front of the saps. Generally they had wheels on them and were moved along as the engineers advanced the saps towards the besieged but I choose to show them dug into the dirt. These were made and cast in metal by Murdock:
The defensive trench also got some sharpened stakes to slow down the assaulting enemy. In By The Sword Divided they called them "Swedish feathers" but they didn't really look like how Swedish feathers are usually interpreted:
Then just this morning the trenches and earthworks got coated in a mix of Sculptamold and thinned brown paint (Sherwin Williams Half- Caff for those interested):