There's many ways of making molds and pouring resin baits, this is just what I do.
Most of my baits, especially glides, have wider shoulder/back than belly or stomach area. Those wide shoulders create a high/higher center of gravity. When I have an even density pour, meaning MB's{micro balloons} are mixed evenly thru the resin, the bait will want roll from side to side as it swims/glides. I don't want or like that roll in a bait. Hooks, split rings and hook hangers alone, are usually not enough to counter the higher center of gravity.
I pour with the molds vertical, belly/hook hangers down, dorsal fin on top. I pour thru a small spru hole on the top of the mold.
I place my weights and hook hangers in the bottom of the mold prior to pouring. I pour with the mold on a digital scale so I can pour exact amounts of solid resin to the gram.
I mix my resin amount for the whole bait but only pour about 25% solid resin in the bottom of each sections mold, enveloping the weights. I then quickly mix the correct weighed amount of MB's into the remaining resin and fill the molds with the MB'd/less dense resin. This creates a heavier bottom/higher density and a lighter/less dense top of the bait.
I find the upward migrating MB's help this process. Unfortunately it also creates lots of bubbles and small surface imperfections in the top/back of the bait that have to be filled.
The heavier bottom/lighter top helps the bait orient itself quicker upon splash down/landing and will help the bait swim and glide more upright/ vertical with less or no roll. It also helps the bait swim and cut from side to side better.
Engineered Angler on Youtube has some vids on pouring resin baits with MB's, worth the watch.
Hope this helps...