After carefully marking the longer base 1 x 2 that spans between the Buckets the precise position of the two 3" long 1 x 2s required to keep a little bit of tension on the handles of the Buckets, at least to the point that the handles are off the ground, but not so much as to cause the Buckets to be cocked with the base of the Buckets too inboard.
See pic:
Bucket base retainer 1 of 3. noticing that the base 1 x 2 is not touching the ground because there is a little bit of tension on this retainer.
Drill clearance holes in the longer 1 x 2 for 2 each holes over the center of the two 3" long 1 x 2 uprights, then one at a time drill a pilot hole into the end-grain of the 3" long 1 x 2 uprights. Make the holes spaced about 3/4" apart.
Use either 1+1/2" or 2" long Sheetrock screws. If the screw strips in the end-grain of the 1 x 2 uprights, try a longer screw.
You always have the option of cutting a new upright if you got a soft or unacceptable piece the first time around.
If you saw, or you didn't quite make a perfect 90 degree cut, you could smear some JB Weld "Wood Weld" in the joint, tighten the screws just to the point the JB weld starts to ooze out. Then clean off the ooze, let set 15 or 20 minutes and tighten the screws a bit more.
