Scott, the first thing was to cut a piece of plywood for the top surface of the sub. The sub timber box is not very thick and didn't seem suitable for attaching handles. The plywood was about 15mm thick (say 1/2" or 9/16") and was glued and screwed into position. I then trimmed a little off each corner of the box to allow the corner protectors a better fit.

The carpet is actually speaker box carpet and is designed to be very flexible to bend around the shape of boxes. It came from a place called Clark Rubber here in Oz, but I guess you could get it from a similar type of store that sells rubber mats, outdoor carpet, marine carpet etc. Alternatively check out speaker building suppliers or even electronics/hobbyist stores.

The carpet is glued on using contact adhesive which you can get as brush-on or even in a spray can. With contact adhesive you normally have to apply the glue to both surfaces, wait for it to touch dry then join the surfaces, but with this speaker carpet there is no solid backing and so the carpet is quite 'breathable'. Subsequently I found no need to apply to both surfaces - just the sub. This means you can brush it on the sub and just press the carpet, one side at a time. You carpet right over the port then cut it out with a sharp knife. The carpet goes on as one long strip starting at the bottom middle of the sub and going all the way around.

The handles are screwed down using 25mm (1") countersunk timber screws. This length should be equal to the thickness of the handle plus plywood plus sub box so that the screws dont protrude inside the sub. I normally use bolts for handles but I didn't want to have to dismantle the sub to fit the nuts. With the extra plywood I guarantee these screws will not pull out.

At the moment the heatsink still sticks out at the back, but one day I will make a removable cover that clips on and off easily.

Hope this description helps.
Mark