For the inner plates (5 of the 7) we cut the corners like so:

The holes have a 5mm diameter and the position of the bottom hole should alternate sides between plates from left to right (mirror the plate basically)

The outer plates follow the same principle except for a little "notch" with a hole added on the side of the plate to attach the power cables:

Front and back plates should have the "notch" on opposite sides.

Gaskets will follor the outline of the plates with a 5mm thickness:

You will need to cut 8 of these.

Cut the plates into 120x120 mm squares, then cut the corners and drill like so:

All holes have their centers spaced perpendicularly 5 mm, they have a diameter of 4 mm and except for the top ones they are located in the center of the line perpendicular to them.

The back plate is cut and drilled the same as the front one except that we add an output hole for the gas to escape on the center of the top of the plate and a perpendicular hole to connect it:

This holes have a diameter of 6mm.

Starting with the acrylic back plate stack a rubber gasket and then a steel plate making sure that the holes line up and that the bottom holes alternate between plates:

Add a small section of the metallic tube to the hole on the top of the back acrylic plate and connect a gas line.