What kind of glue and method for the A1-sized gameboard?

3M Super 77 Spray adhesive. It will let you adjust the alignment and evenremove the whole thing if it's not correctly aligned at first try, but after a few hours it will be strong. Do some tests first to find the right amount. Too much usually means lumps. Too little and the thing will not be strong enough. If the cardboard is too absorbent, you might need to spray both surfaces.

but note some important points:

1) Make sure your working base is absolutely flat (no small particles, offcuts etc.. lying around).

2) Cut small point marks in your poster along the printed crop marks. This will help you place the cardboard once your poster has been turned face down onto the table

3) Apply glue spray (using 3M quoted above).

4) Lay your paper face down on the table. Try making a 'jig out of fixed cardboard pieces so your paper is put in the same spot every time, and it doesn't move during the critical placement.

5) Now align the cardboard edge (the edge closest to you) with the cut marks you made in (2).

6) When cardboard has been perfectly aligned with left and right cut marks push the cardboard down very gently onto the paper just so the paper begins to stick to the carboard (but do NOT push all the way!!)

7) Now turn everything over so the cardboard is against the table, and the poster is face up towards you - but still being careful not to let everything stick together.

8) Take a large flat, smooth and clean 1 meter ruler and very gradually push it along the poster to evenly apply it to the cardboard base. Take your time, and use the same speed and pressure right up till the end.

9) When the poster and card are one, turn the whole job back over and trim along the cardboard edges from behind the poster.

10) Smile! Now you have a nice game board!

For 'homemade' boards like this you should increase your margin for error and make the bleed about 5-6 mm each edge. Also, in your design work, make sure that any important text or images do not go too close the game board edge. To be safe, keep these elements 10 mm from all edges.

Remember, just poorly aligning your card at the beginning with the slit crop marks could mean 3-4 mm out of synch at the other end.

Good luck!

You may be spraying the glue too heavily.

1 sq meter is just less than 11 sq feet

I use spray glue for mounting boards, cards etc.. In the last year i have made 5 18x18 inch boards for one project, several dozen 8-1/2x11 inch pages worth of tiles/components and several hundred poker sized cards and still have a bit of gluing left before my can runs dry.

The boards and tiles together are about 26 sq feet. Adding in the cards seems that im getting a lot more from a can then you are. Also with the currency rate of 1 EUR = 1.44517 USD you are paying 2 times as much for your glue as I am so you might try to find another source.