What ever container you're using, when you 'pack' the parts,,every surface must be in contact with the char.
But you do not want to compact it to the point of crushing the char into dust doing it.
As you place the parts in and start adding char around them,,bounce and rock the container to settle the contents. We made a $#*! of a racket packing the boxes up as it was done on a steel table.
An inch of char surrounding each part and extension off of a part is best. You can get away with a little less but not much.
Our boxes were a couple different sizes. But they were both shaped like a flower box looking from the end. Wider at the top than the bottom by just a bit,, the smaller box about 14" long, height about 7".
In that small box we'd do a complete shotgun frame w/ forend, top lever, trigger plate (installed on frame) and have room for a Colt SAA frame w/ gate & the hammer.
No spacers or shields on the parts. No anti-warping braces.
The box's cover was removed while the box was still in the oven. A quick series of movements to open the furnace, remove the cover and put it aside, change implements (forks) and now hook onto the box itself.
Lift it out of the furnace, walk w/it over to the quench tank, set it on the support, close the shield, and overturn the box.
Wait the 5 count and pull the pin holding parts on the wires so they can sink to the bottom.
About 12"+ drop from inverted box to quench surface. Box was always overturned from the same distance above the quench as it was rested on a support.
A steel shield was pulled into place just before to protect from steam and splatter and an outside vent took most of it out. But dangerous for sure if you're standing there unprotected.
The same cadence was carried out each and every time to get uniform results. Changing anything from beginning to end once you have a routine that yields good results will most likely alter those. Sometimes it can be the smallest of changes.
Again it's not the only way to it, it was the way we did it and got the results we did.