Help please, tips on aligning double sided for engraving

Dear all
Does anyone have any answers to getting great alignment for flipping work over (3mm ply) and aligning ‘perfectly’ for engraving the other side? I’m trying to engrave some tokens, same image on both sides of a coin size cut out. There are 30 tokens evenly spaced on a grid.
I’ve tried scoring a perimeter line on card then placing the work on top, this isn’t very accurate due to wobbly card and also likely a fire hazard once the cut starts.
I’ll go to sleep thinking about some sort of jig.

Thanks all, hope you are all well

Why not use the same piece of plywood you use to cut the actual item out, i.e. the “first page”? This is the way I always use for symmetrical items, it is super easy, cheap and accurate.
I use 3 layers for the projects, cutting layer, front layer and back layer. The first page is engraved, this layer is turned off, now I cut out the items and turn off this layer and use no. 3 layers for the back.
The plate itself I clamp down, with the one 90 degree angle in X = 0 and Y = 0 on an angle-fixed frame I have on my laser bed. For me there is no problem with taking the whole plate up and mounting it down to X/Y=0:0 again if I need it, it fits perfectly and is very accurate.

Thank you I think I’ll have to go down this route. What do you use for your angle-fixed frame? I have an aluminium bed.

On my K40 I use an extremely simple device, 2 pieces of wood screwed on my nail bed in 90 degree.