If you have a multi-speed bike with a gear tree and derailer, put the bike in the highest gear.
In other words move the derailer the most outboard it can go, positioning the chain on the smallest diameter sprocket.
Rest the the bikes axle extenders on the 2 x 6s that are screwed to both the starboard and port Buckets.
Be sure you are set up on a level surface and that both Bucket edge lips (the opened side of the Buckets) are in full contact with the ground with no sideways cocking.
On the port side position with the 2 x 6 resting hard against the outboard face of the axle receptacle.
On the starboard side, position the Bucket so the 2 x6 and or bucket are no closer than 1/8" to the derailer.
Make sure the axle extenders are centered on the 2 x 6s on both the starboard and port side.
Then take two of your recently cut 1 x 2 x 5+3/4"s and position them on the starboard side with the end-grain resting on the face of the axle receptacle and tightly resting the long way against the axle extender. Each 1 x 2 gets two Sheetrock screws (either 1+1/2" or 2").
Position the inboard screw 1" outboard from the end-grain edge of the 2 x 6 and the outboard screw 1" inboard from the outboard end-grain edge of the 1 x 2.
Pre-drill the 1 x 2s with clearance holes then screw the 1 x 2s into the 2 x 6.