Here's a tip we found years ago for filleting fish - Fish Velcro!
Simply get a few feet of outdoor carpet - the plastic, artificial turf they sell at the big hardware stores. The carpet works great - just like velcro, to hold the big fish in place as we fillet them.
We keep a few feet folded up in the boat for when we are camping...
The rubber backing also graps onto the log, cooler, or table and is fantastic to keep that fish in place.
A few dollars of carpet will last for years. The green is easy to see if you get a fleck on the meat, and makes the meat look perty...
At home, we stapled a 2x3' piece to some 1/2" plywood. Light and easy to move and use.
This piece is 4 years old, and going strong.
Cleanup is a breeze - blast the chunks off with a hose, and the blood runs right out, too. After the hose-blast, we spray everything with bleach or cleaner.
Good as new, and ready to get used again!