I once built a megabeast zoo, glass-walled fully engraved enclosures with feeding hatches a level above. I had five or six FBs, two ettins, a cyclops and a dragon as far as I can remember. Wish I'd saved pics of my FB trap designs now. Basically I had a couple of untamed GCS (who were also used for silk farming), and I would dig out a sort of loop tunnel with drawbridges, so that I either had a short straight route open to the cavern, or a longer route that forced you to go round via the spider and a line of traps. The spider's cage was built in a pillbox with a pet-impassable door, and a hoary marmot installed on a chain just outside. When freed by lever, the spider spat web at the marmot, webbing the traps installed behind it. Then I would pull a lever to lower a bridge allowing the spider to exit the pillbox, and the spider would try to walk round to the marmot and get recaptured in another cage trap. Now I had two or three webbed traps, so I pulled the next lever, opening the loop path to the caverns. The beast would try to path to the hoary marmot and be caught in the webbed trap.
I remember it took a LOT of micromanagement, and dwarves (especially children) just loved to run down there for absolutely no job related reason and get themselves caught in the webbed traps, which would cause a lot of cussing on my part as I would then have to start the whole process over. Once I'd just gotten all three traps webbed up after twenty minutes of dwarf-wrangling, a hauler came down to get the spider and her three children ran straight down the trap tunnel before I could lock them out and got themselves all caged in a row, one two three. Start over! I was sorely tempted to order those cages dropped in the volcano.