54th Siege Battery Royal Australian Garrison Artillery, near Ypres, 12 September 1917. These guns were deployed near the Ypres-Comines Canal, at the base of the Ypres Salient, which accounts for them not being dug in. Camouflage material is behind the men moving shells along the light railway, so presumably the netting was down for this bombardment mission. Some aspects of the amount of labor needed to ready an artillery position can be seen. Heavier weapons benefited more from light railways because they had heavier shells (200 pounds for these eight-inchers). Each of these howitzers has a substantial quantity of shells, and there were dozens of eight-inch howitzer batteries in the Ypres area. The platforms under each howitzer (to spread recoil and prevent the howitzer from sinking into the soft ground) had to be brought to the site and put in place; the planks could be six to eight inches thick.
It took a substantial amount of time to build light railways, especially if the ground had to be stabilized before the rails could be laid. Plumer benefited from dry weather during his attacks in September 1917, which made the infantry's job easier but also improved his logistics situation.
Source: IWM photo E1918.