I did not like the pan design on the one you showed. I prefer a small opening at the center on the bottom edge of the pan, and "diagonal" pieces across the corners to help "funnel" the wax towards the center opening. The seams should be soldered to prevent leakage.
To get the best use out of your solar wax melter, first wash the comb/cappings to remove any excess honey. The honey water can then be fed back to your bees if desired. If you can't wash the comb/cappings, and/or still have honey in them, you can add some water to the bottom of your catch basin. The wax will rise above the water and any honey or other debris. If you have a lot of debris you can then just scrape it off the bottom of the cake of wax once it hardens.
Best tip- ask your wife/girlfriend/female co-worker to save her old pantyhose for you. Place the wax in the pantyhose and lay the whole thing in your wax melter. The wax will be strained through the hose as it melts and the gunk will be trapped in the hose. When the hose is too gunked up to use, just toss it and get another pair. This won't help with the honey, but it will get rid of gunk.
Another thing that I do is to line my pan with "Black Wrap", which is a very heavy duty, black aluminum foil which we use in the entertainment business. It is tres expensive, but it lasts a long time- I maybe only change it out once during the season, depending upon how much wax I am melting and how clean the wax is to start with, -a roll has lasted me several years so far. You could also use plain old aluminum foil as well- I just happen to have the black stuff which I like because it helps with solar gain. Either way, it keeps the pan nice and clean and you can just toss it when it gets too gunky.
On my first solar wax melter I used a piece of mesh across the opening- that worked okay till the mesh got full of gunk- then it was a hassle to clean. Can't remember exactly- maybe I did it in a way which made it difficult to replace the mesh?