I cut all the 2x8s to exact 10' length, traced a pattern for the end cuts, and used a jigsaw to cut them out, allowing for a 12" overhang past the post. I then laid out the single crosspieces on the posts, used a spade bit to create a countersunk pocket, and a 5/8 auger bit to drill bolt holes through the 2x8 and the 4x4 post after making sure to square up the two pieces. I laid out the slat pattern on the side pieces, and screwed the brackets in place. Next I drilled pockets and bolt holes in the outer beams to serve as guides. I then stood the end assemblies upside down on the driveway, clamped the side pieces in place, squared up the pieces, drilled countersink pockets on the inner beams and drilled the bolt holes through the post and inner beam, and bolted them in place. I now had a mostly complete arbor, although upside down. I cut 7 saddle notches in the center beam to hold the slats firmly in place, and measured the width for the slats and cut them to length, and cut a saddle notch where they would cross the center beam. I then labeled the corners and disassembled the side beams to transport it to the back yard, leaving the end assemblies (one crosspiece and two posts) intact.
Next I did site prep for the concrete piers, measuring out my 8'x8' square, and leveling out and tamping down the dirt under each pier. After the piers were level and square, we put up the two end assemblies (you will need two helpers, or use 2x4 prop boards temporarily screwed to the posts), then laid the side beams over the end beams and bolted them in place loosely. After all the beams were in place, we trued and squared it up and tightened all the bolts. Some adjustment to the pier position is likely. The center beam was installed using right angle brackets, and the slats were slid over the center beam into the notches and secured on the ends with right angle brackets.
The end result is quite good, with minimal material and no complex construction. It can easily be made with a circular saw, a jigsaw, socket wrench and screwdriver, although I also used my chop saw. If you are interested in plans of the Arbor or any other projects, contact me about this or any of the projects you see on this site.