question

Process Flow will definitely help in this situation. What I would do, is have a List of the 100 slots (you can initialize this at the beginning of the model in Process Flow as well.) Then when items reach a certain point on the conveyor, they pull the slot from the List based on whatever criteria you want. And then just do a conveyorsenditem command (this can be selected from the custom code activity in Process Flow), to send the item to the designated/pulled slot. Then you just need a "Max Wait Timer" of 0 on your PullFromList activity. This just tells FlexSim to pull a slot off the list, and if there aren't any available the max wait timer fires, and you can redirect the token to another different activity that will just send the Conveyor to the loop.

I've created a small example that demonstrates this. This example uses a Resource group instead of a list, but the concept is the same:

dploop.fsm

If you are unsure about Process Flow, I highly recommend going through the Process Flow tutorials in the manual. (User Manual > Tutorials > Process Flow) They will help you get a basic understanding of what Process Flow is, and you can set it up and connect it to your 3D model logic. I think you will find the lesson on Lists particularly helpful.