When I etch a prototype circuit board I usually try to use less ferric chloride I can. This means to pour only a thin layer of acid in a flat container, and keep the copper surface submerged in it.
I noticed that keeping the copper side upside-down speeds up the process. The reason is the spontaneous change between reaction slag and clean liquid, but some space is needed to let it happen. For this purpose I built some holders to keep the pcb lifted and to handy raising it to check the process evolution.

Step 1: Material

Actually the idea came from some plastic socks holders, which are perfect for this project. You can probably find something else which fits right, you also can glue together coffee plastic sticks. This plastic mellows with the heat of a candle, so that you can mold it very easily.
Cut the arms at the right length with a little metal hacksaw. For this holder I designed a H shape, so that there will be four anchor points to the board, and an "handle" to keep them joined.

Step 2: Molding

Over a flame heat the plastic in the area you want to bend it. Then mold the four arms with a U shape. The longer the arms are, the more bendable they will be, so that they can fit more pcb sizes.
After heating the braces extremities, with small pliers make a shape where to keep the pcb edge.

Step 3: Build an Entire Family

Check that your new holder fits your pcb, and eventually build more ones to operate with different sizes of boards.
You can also build two-arms holders for tiny circuits. I actually built this last holder to etch my future nixie clock circuit board.

Step 4: Ready to Etch

With the help of your new tools the etching process will be easier, faster, cheaper, and also less dangerous since there is no danger that boards slip from your grab. Remember to change every 10-15 minutes the position of the holder shifting it, so that no fluid remains in small areas where otherwise the process could take longer time.