This is hopefully a simple one

I may have to replace some woodwork over a window which has lead flashing
folded over it at the top

The lead flashing is set into the mortar between courses of bricks and folds
down by around 3" vertically over the wood.

So my question is :-

How is the flashing usually fitted between the bricks? I'm assuming it is
inserted where the mortar joint would be by a couple of inches and fixed in
place using some kind of adhesive/sealant - Is this correct.

I'm planning on removing the old stuff and then angle grinding the joint to
open it up to fit new - Would this be a typical way of doing it?

Any advice on this or recommended materials would be appreciated.

Thanks

R