There is something iconic about the image of rank after rank of Imperial Guard (Astra Militarum to our younger readers) fighting the enemy from a large trench network. After reading the fantastic "Straight Silver" Gaunt's Ghosts novel, I was inspired to create a trench network for my own guard army to fight over and defend.
The idea was to create a modular trench network, made up of 1 foot square sections. This would help both with storage and with variety, as I could re-arrange the battlefield to save me fighting over the same layout over and over. I decided to make eight sections, as this would allow me to deploy the trenches in a 6' x 1' arrangement for a long board edge or in a 4' x 2' arrangement for short board edge fighting.