Lay them flat and attach them together with the tongue and groove until it's as wide as your door opening. Next, frame the shiplap with 1 X 6 pine, hold in place with clamps at this point.
Now cut your diagnoal pieces and place those on the door. When you're sure everything is aligned, attach the frame pieces to the shiplap using a countersink bit
Measure and mark where you will need to drill holes for the barn door hardware. We also routed a 3/8 channel on the bottom of the door for the door guides.
We drilled the holes for the hardware but didn't attach it until after painting the door.
We purchased a barn door hardware kit on eBay because it was far less expensive than most other kits we looked at. It came with everything we needed including the floor guide.
Lastly, we installed a piece of oak on the wall to attach the barn door hardware to. We painted the oak the same color as the wall so it's basically invisible.
Building this door ourselves saved us hundreds of dollars!