This is what I do using t-nuts. It's low tech and cheap and not too difficult. But it's pretty strong enables you to get high precision without high precision tools.
I've used it on the last couple of pocket board I'm using where the bolts are countersunk and need to line up exactly.
Here is part of a paulownia wingfoil board I'm building (covid downtime), but it's exactly the same as I've done for the paulownia pocket boards.
1. Drill oversize holes, but narrower than the flange of the t-nut and slightly tapering.
2. Put the base plate on the board and bolt the base plate where you want it to go. Make sure the bolts go in straight. So we use the baseplate to get perfect alignment. Tighten fully so the t-nuts are in as far as they can go.
3. Unscrew bolts to remove the baseplate. Take care not to dislodge the t-nuts as you do.
5. Cover the area around the holes on both sides with masking tape and remove the tape over the holes themselves.
6. Mix some resin with filler (glass or whatever) so that it's a bit thickened still slightly runny.
7. Pour the thickened resin into the holes.
8. When it's set a little, screw the bolts in from the other side (the deck side) and leave them there for a while.
9. When it's set a little more, unscrew the bolts. Wipe off the epoxy. Coat the bolts in vaseline. Screw them back in, this time from the base plate side.
10. Every so turn the bolts a little to make sure they still turn.
11. After an hour or two, when the epoxy is sure to be not hard enough to not flow at all, remove the bolts.
12. Remove the masking tape.
13. Wait for epoxy to cure.
14. Carry on with the rest of the board build, glass over the t-nuts.
You end up with the t-nut being fully bound into the wood with an epoxy plug.