Is there a LEGO clamping tool?
If you’re using regular bricks and plates, there is really no sure way to tightly lock them together. The only way to ensure secure assembly is to use special or Technic pieces.

If you use special bricks with “knobs” separating each row or layer with two rows or layers of plates, you can then use plates across the knobs.

A more secure assembly would be to use Technic bricks with connector pegs, separate each row with two rows of plates and use Technic beams across the connector pegs.

If you have a wall structure that is two units thick you can also use bearing elements which are 2×2 bricks with snaps.