If I were to make them I'd use a candy thermometer and cook the syrups to 260-265 degrees before adding the solids. Keep it on the heat and stir until its all mixed in well then pour into a metal container like loaf pans. I'd use cooking spray to line my metal containers so I can dump out the block once it cools.
I see your cooking spray and raise you a parchment paper. Just lift them outta the pans and use the paper they're already in to wrap them with. And not have to clean nasty baked on cooking spray off your pans.
Fair enough, that wrapper wouldn't hurt a thing if it peals off once they are set hard.... but I wouldn't bother to wash them,,, I'd have dedicated pans for deer and save the ones in the kitchen for bread. That is if I were going to make deer blocks. Also the cooking spray doesn't cook on. I know this because I do use it on our good cookie sheets to make toffee and peanut brittle, at Christmas time, which are over 300 degrees when they get poured on. The spray washes off easy with warm soapy water.