Yep, as
@D Cluley said, install the back first, then the front overlaps it. There is not much overlap, so be careful that you don't pull the front section too far forward while fitting and wind-up with a gap.
Fit both sections from the center hump outwards. Do not fit the door sill areas until the end. I used paver bricks inside plastic bags (because the pavers were dirty) to weigh down the carpet so it would flatten out and conform better. Where it still wouldn't settle, I used polyurethane construction adhesive (sparingly) to keep it in place, then placed pavers over top while the glue dried.
The usual instructions say to cut star-shaped slits approximately where you want holes to be for seat belts, seat mounting, etc. Then get the exact hole positioning and cut larger holes. If you have a soldering iron, it works much better and faster. (I think I got this tip from
@Big_John .) Just make sure you have good ventilation to blow away the burning plastic smoke, and a rag to wipe the melted plastic off the soldering iron to reduce the smoke.
For seatbelt holes, I found the correct spot, poked through the carpet with an awl, marked the spot with a black sharpie, then poked the iron through the same spot to enlarge the hole to the correct size. For seat mounting holes, weight the carpet around the hole area with pavers, then climb underneath the car and poke the iron up through the hole from underneath.
