If you weren't already familiar with the builds that use the barrels outside I would encourage you to look for VoD's and videos that use them, but outside you're building on the barrels along the wall. The reflects will need to be a tight 2+1 to get everything in the DU count
The inside stack Mortars are for the table closest to where hint #2 is, and the phys beam is to block off the portal spawn mobs.