I am cutting some 2x4, 2x6 and 2x10 boards to put in our flash board system. I need to know what to add to be able to hook a T bar or crow bar to them to place them in it and remove them. any ideas?

I'm not familiar with flash board installs, but could you drill a shallow blind hole (or two) in the boards that would allow a piece of all-thread to be screwed into it, install it, and then unscrew the all-thread hence removing your installation tool? Just bouncing the idea off of you. If you needed it to be long lasting for future removal, maybe a stainless steel nut like this from McMasterCarr...

https://www.mcmaster.com/#98007a033/=19h9khq

could be recessed and screwed to the boards using the holes in the mount plate.

Stainless steel hooks on both ends such as this?

https://www.grainger.com/product/MONROE-PMP-Screw-Mount-Utility-Hook-1-4HDW4 (these aren't stainless but you get the idea.

we have several agridrain risers that the plastic stoplogs have a similar hook to pull them up.

or perhaps screw in a lag bolt and leave an inch protrude to hook onto.

For our "boxes" or flashboard risers we use 2x6 tongue and groove boards. We build our boxes with a channel for the boards to slide down. You simply drop them in. We fab a hook from rebar that is similar to a hay hook.

Using a hay hook, you probably could use a forster bit to drill a hole part way into the board to give you a place to hook the point of the hook on.

Maybe one "hole" on each end of the board instead of one in the middle?

Our hook is hammered flat kind of like a flat head screwdriver. With the correct angle it has no issue pulling boards. It even works on our 150" long spillway boards.