First model your gingerbread people on a scrap of plywood in clay. We made a boy and a girl with fine details - since they will be on a wreath around the front door.
Two reasons why we chose latex molds for this project were the undercuts on the mold, and the casting material (Durham Rock Putty) that sticks to straight plaster molds even if common mold releases are used. Undercuts are the bane of rigid moldmaking. The gumdrop buttons and piping along neck, wrists, and ankles all would lock a rigid mold to the cast material. Latex molds flexibility is good for undercuts but won't keep it's shape for filling, so we used a plaster cast behind for rigidity.
Hot glue strips of cardboard around the finished clay masters to create a box around each figure. This contains the latex but mainly is for the plaster backing pour. It just needs to be tacked in place, the first coat of latex seals it in place, but make sure it is tight against the plywood.
Follow the instructions for the liquid latex to lay down multiple layers. Be sure to push the first layer underneath all of the undercuts with your brush and pop any bubbles formed against the clay master. They recommend 8-16 layers with some drying between. We didn't put in any strengthening cloth but you can if you have something that might tear or you are producing hundreds of items. We ended up laying down 10 layers and used up half of a $20 container - so $5 per gingerbread person was great though a bit time consuming vs. 2-part one-step $$$ molding systems.
When the latex has dried. Fill the cardboard dam with plaster of paris. Strip off the cardboard then the plaster and latex should unmold nicely.