When do you cut your hinge slots? before or after covering? I usually cut mine before covering then I hunt for the slot and use a heated Exacto knife and melt the covering.

I usually cut my slots after covering (or drill my hinge-point holes). No particular reason, that just seems how it turns out. I will determine where I want my slots (or holes) before I cover it, that way I can be sure I miss rib attachments and such.

it's easer to do them after covering. In a perfect world your covering job wouldn't effect the pieces being covered, but in the real world you'll probably put a very slight warp in at least on piece so getting it to re-line up after you've covered the piece could become a problem

I cut all slots before covering and make tick marks on the plan so I have no trouble finding the slots after the covering is on. I slit them open with a #11 blade and use a 15W soldering iron to seal the area around the slot.

I cut 'em before covering (as indicated on the plans), then cover it. Finding the slots is easy if you use a straight pin or gently cut along the area with a # 11 blade - once you cut through the covering and hit the slot, the knife slides in easily.