You will need (local lowes prices here)
Washer tray 25 dollars for a 29x31 (they had a larger one for 10 more)
Ceiling grate thing 9 bucks.. in lumber area with ceiling tiles
Zip Ties - 100 for 4 bucks
Astro turf stuff. Heres where it gets iffy.. they have green, blue and grey... they have thick and course, or smooth and soft. I chose the thick because I did not want to have any association with carpet at all. Grey was only because eventually it will go on my porch and i want it to blend a little bit. The underneath was also made like regular carpet so it eliminated the need to pop hole for drainage unlike the base of the green stuff which was more grass like.
The grey astroturf stuff cost me 4 bucks a linear foot and I got 2 feet (2'x6' gives me 2 extra squares for later)
Total cost around 41 dollars
Step 1: Step One
You need to cut down the grate. I tried using the scissors but it just snapped the plastic. I figured out halfway through that a pair of pliers and a twisting motion snaps the pieces right off separating the sides.
I personally would measure one square less than needed as mine was a little snug when put together.
What I did was lay the grate on the top and guess at which square to chop at. Plan on losing a whole square where you cut/snap it.
After you get the main part cut you will have to cut the spare up and piece the ends together.
An alternative I found online is to use metal but I could not find any sturdy enough.
Following the cut out, take your zip ties and attach the pieces together to make a nice almost square. It should fit in your tray with a tiny room to spare on each side, if not trim the sides now.
Step 2: Time to Carpet!
Unroll your turf and if its a straight cut you shouldn't have to trim much. Mine wasnt. AND i started attaching it to the grate before I realized which left a tiny bit not covered. But thats ok. I'll fix it later when its time to change the carpet.
Set the grate on the carpet.. make sure all edges are lined up and trace it with a permanent marker. Trim off all excess using a razor blade or exact-o knife.
Using the exacto knife pop a hole in the corner (second one in diagonal.. here it is ok to skip a square) and lace your zip tie through and secure. You may also do the halfway point between corners.
BOY DOGS if you have a boy dog and anticipate him marking you may want to get some pvc and secure it (drill holes in the end and run zip tie through in a cross pattern) to the center of the mat.
Step 3: Step Four
Another option is pee pads under the the grate or hospital pads which you can wash daily.
I have been told using a watering can with hot water every day and bleach once a week keeps any smells away.\
Getting a pee soaked paper towel under the grate (the dogs pee not yours!) will attract it to pee on the turf. They also make attractants you can buy at your local pet supply store...
Now to build a crate!
Good luck training!!