The PCB is a custom designed component, therefore you will need to order this part from PCB manufacturers like https://oshpark.com/ or https://jlcpcb.com/.  The gerbers I have attached to this project are very conservatively designed in order to be directly compatible with these services.  You should be able to simply drop the zip file into the website and select the necessary settings.

From JLPCB:

Track the production progress and shipping until the boards arrive:

The rest of the BOM items are off the shelf devices, therefore you can purchase these from a number of sources like https://www.digikey.com/ or https://www.mouser.com/.  The BOM I have attached to this project show Manufacturer, Manufacturer PN & Quantity:

Manually load these parts into a cart and purchase the components.

Once your PCB & components arrive, you will be ready to start assembling.  One critical custom tool will be the solder paste stencil which can be ordered using services like https://www.oshstencils.com/#%20.  The gerbers I have attached to this project are very conservatively designed in order to be directly compatible with these services.  You should be able to simply drop the zip file into the website and select the necessary settings..

From OSH Stencils:

Track the production progress and shipping until the stencil arrives.

Also you will need solder paste.  I recommend using lead free, but be sure to investigate all of the usage warnings since it does contain chemicals.  I usually purchase my solder paste through OSH Stencils during checkout, but you can buy solder paste through many sources:

The first step will be to secure the PCB to a flat surface in order to apply solder paste:

I highly recommend the Acrlyic Jig Set offered by OSH Stencils:

Keeping the PCB still while applying solder paste is going to be critical in order to ensure good paste application.

You are now going to align the solder paste stencil with the PCB and tape the solder paste stencil down using masking tape:

Take some time to review this alignment to ensure you get good paste application in coming steps.

There are many tutorials online on how to do this.  Here is a simple explanation of what I did.

Start by applying a large bead of solder paste above all the openings:

Take an old credit car (or one supplied by OSH Stencils) and smear paste at an angel in a top to bottom direction.  I have learned if you can do this in one solid pass you get pretty good results.  Please refer to online tutorials for more information, this step comes with practice.  Long story short you want to get adequate paste in all open apertures.  Once you have done that, simply hinge the stencil away from PCB:

Take some time to review your paste application using a USB Microscope:

Make sure you have good alignment and paste quantity.  If you have a few trouble areas you can either touch these up later, or start over by cleaning off board (or using new one) and repeating steps.

Now you will need to clear your nerves and grab some tweezers.  You are going to have to manually pick and place all surface mount components onto the PCB.  Use the reference designator on BOM to translate to the correct reference designator on PCB.

If the footprint has paste applied, then you are going to want to place this part now.  If they footprint does not have paste applied, then you will want to solder these parts in the next step,.

Its worth noting that the placement does not need to be absolutely perfect.  If each terminal is in contact with the right pad on the PCB, then any slight imperfection should be corrected during the reflow stage.

Your PCBA should look like this once all surface mount components are placed:

Once again use a microscope to review your component placement: 

Feel free to nudge or replace parts if alignment is not adequate.

Reflow all solder paste using a hot air gun.  There are many tutorials on this as well online.  My main tip is to make sure air flow isnt too high where you have to worry about parts moving.  Simply take your time and make sure all solder has reflowed and parts are soldered:

Inspect all solder joints using a USB microscope:

Locate all remaining materials and one by one hand solder each through hole and heat sensitive component to the PCB.  Your PCB should look like this when complete: