I forgot if you are filling the cakes or just spreading jam on them and then glazing them.
If you glaze them while they are frozen, it will go that much faster.
For set up, I would use a sheet pan (or jelly roll pan) lined with parchment paper. Then put a cooling rack on top of that. This is where the cakes will sit until you move them onto a board - either a big half sheet board where you will line them up or on mono boards that they make specifically for individual desserts. You can buy half sheet boards and boxes at a cake supply place or ask at a local bakery if you can buy some from them. You will want at least 4, if not 5 boxes and 10 boards. The extra boards are just to have on hand in case you need them.
In terms of glazing the cakes, if you make the glaze in a bowl, and your cakes are frozen when you start to work with them, you can just dunk them in the glaze and tap off the excess with a small, wide pancake turner. I’ve forgotten if you are layering the cakes with jam or coating them with jam and then glazing them. Dunking means they will be evenly covered and the mess will be all in getting them out of the glaze and getting rid of the excess. Then put them on the cooling rack over the parchment. The glaze will drip onto the parchment, as the cakes sit and it will firm up over time. Then using a spatula, you move the cakes onto the half sheet board or use a little buttercream or jam on the mono board and put the cake on the mono board. Then you will just pick up the sheet of parchment, fold it in half like a piece of pizza and then squoosh all the glaze on the sheet back into the bowl. You can put the bowl over a pan of simmering water just to loosen it up a little and make it more fluid. Don’t over heat this or it will break.
If this method doesn’t work for you, then put the unglazed cake on the cooling rack (start at the far left corner and work your way down or across, one lane at a time). Using a ladle, pour some glaze over it. Because they are square, the corners will be the hard part so I would practice with the dunking method to be honest with you. Pouring glaze on a round is easier than doing a square.
Keep the cakes frozen to make it easier on yourself. Work with a dozen or less at a time.
I think you will need to make at minimum 3x the original batch size of the glaze and quite possibly four - so have ingredients on hand to make five batches so you will not stress in case you end up using more glaze than you think. Make the batches individually instead of all at once, it goes really fast. When you make a fresh batch, after you stir it, add the excess from the previous batch. Use a strainer set over the fresh batch so you capture any crumbs from the used glaze and sqoosh out the parchment paper into the strainer.
If the worst happens and you are unhappy with the way it comes out, get some good quality cocoa and a fine strainer (like a tea strainer). Very lightly tap some cocoa on the tops and no one will notice any imperfections if there are any. You want a very light hand with this, otherwise you can end up with a worse mess and big clumps of cocoa instead of a fine dusting
Mono boards are available from Pfeil and Holing (http://www.cakedeco.com and probably Country Kitchens and other pastry supply places.
Once the cakes set, then put a dab of jam or buttercream on the mono board and place the cake on it. Use a loop of masking tape to secure the mono board to the half sheet board if you are using that to transport.
I hope this makes sense!