Measure the garden site you have chosen for the bench and trim reclaimed flat boards to the correct length if they are too long. Measure two or more widths of board and cut cross pieces just slightly shorter than that measure from the discarded ends. Screw the cross braces to the underside of the boards to create a flat platform.
Haul the connected boards and a load of old bricks to the site for the bench in a wheelbarrow. Use a shovel to dig out any uneven sections of the ground and a level to make sure that the bench will sit flat when installed.
Stack the bricks on top of each other to make two supports, one for each end of the bench. For greatest stability, set one row of bricks pointing north-south, and the next row pointing east-west. Alternate the direction of each successive row until you reach the height for the bench. You may mortar the bricks in place, but stacking them crosswise makes this unnecessary.
Check one last time with the level to be sure the brick platforms aren't at a slant. Place the connected boards on top of the bricks. Set a couple of big stones from the property on the bench at either end to anchor it, although, under most conditions, it will sit solidly in place.
Set some old pavers or broken flagstones in a random path leading to the bench and plant around it with ferns, perennial climbing vines on a trellis and weathered pots and planters of annuals. Keep some cushions near the back door to grab en route to the garden seat.