If using universal PCB just solder all the components as per Schematic.

Provided Gerber files can be used to get board manufactured. Alternatively PCB can be developed using home methods. PDF printout of the copper can be used.

Board is design to be programmed with AVR MKII programmer. Available software can be used to program micro controller.

I'm using AVR Studio.

3D print enclosures using STL files provided.

Fit board to printed enclosure and magnet to the other one.

Now device is ready to use. Can be mounted on entry doors, fridge door or any other places where alarm is required after certain delay.

When battery powered check if LED turns on when magnet is away from the active parts enclosure and if sounder is activated after give time (30s).

I used Farrell to buy components but they can sources anywhere. Coin Battery holder is for CR2032 battery