Arduino Controlled Relay Box

Step 5 Complete the outlet box

Now you've got everything connected all you have to do is close up the box.  Since you already threaded the extension cord you should be able to simply pull everything into the housing.  Pull the control wires out the other side of the box and push the relay board to the bottom.  Put the outlet on the top and screw it in, finishing with the top plate.  If you have stickers that say "GFCI Outlet" you can put them on the sides of the box at now and move on to testing.