Necessity is such a mother. I'm sure others have this same problem. I'm just surprised nothing existed to do this job.
This shelving solution is not intended to be moved while full.
It is also not intended to have heavy boxes at higher than the second shelf.
This solution is comprised of many identical units, each weighing only a few pounds and costing under $4 each for materials.
Each unit connects to the ones next to it in every direction (left, right, above, below), providing more stability.
It is assembled and disassembled all from the front. Kids can help!
The end solution can be any custom shape to fit under tables, mantles, windows, or other architectural objects.
No shelving solution I could find offered me the density and flexibility that this solution offers.
Step 1: You Will Need
plywood - 3/8" thick
top 10-1/2" x 20"
doorskin - 1/8" or 1/4" thick
bottom 10-1/2" x 20"
furring strips - 3/4" x 1-1/2" by usually 8' long
out of furring strips, cut the following lengths:
vertical corner supports 10-1/2" - need 4 per box shelf
back brace max 21" - need 1 per box shelf (angled cut described later)
side brace max 21" - need 1 per box shelf (angled cut described later)
wood screws #6 x 1" - need 12 per box shelf
used to attach vertical supports and braces - 6 pieces, a screw for each end
machine screws #6 x 32 x 1" - need 1 or 2 per box shelf
used to vertically stabilize multi-box shelf system
machine screws #8 x 32 x 2" - need 1 or 2 per box shelf
used to horizontally stabilize multi-box shelf system
table saw - or capacity to cut top and bottom (some home improvement stores will do this for you at a nominal cost)
miter saw - or capacity to cut supports and braces
electric drill and bits
electric screw driver
NOTE: 1/8" doorskin is weak but its job here is to hold the vertical supports straight. It does that well while keeping the total box shelf weight down. It isn't strong enough to support the weight of some boxes but in this use, it will be sitting on the floor or on top of another box shelf, which means it will be sitting on top of a piece of 3/8" plywood, which will provide the strength needed to hold the box.
NOTE: I started out using wood screws #6 x 3/4" but moved up to #6 x 1" for a better application
Step 2: Pre-drill Top and Bottom
Vertical support screw holes -----
The corner holes (pink) for the vertical supports should be centered where the vertical support will go, which is 3/8" in from the side and 3/4" in from the front, outlined in dotted green.
Drill the vertical support holes with a bit that's the diameter of the solid part of the wood screw, smaller than the diameter of the outer edges of the threads.
Vertical stabilizer bolt holes -----
The side holes (purple) are for the vertical stabilizer bolts. Why 8 inches from the front? I just chose a distance that I thought would be easy to reach from the front to assemble and disassemble. I didn't put them right in the front because I felt I could get more stability by placing it along the middle somewhere.
Drill the vertical stabilizer hole as big as possible while being smaller than the head diameter of the machine screws. You'll want as much flexibility for these holes to line up later.
Step 3: Attach Vertical Supports
Step 4: Cut and Attach Angled Braces
I kluged this part. I took a furring strip that was more than long enough, held it in place as close as I could get it, drew a line where I wanted it cut, and cut it with a miter saw. I then did the same on the other end. Trial and error. There was enough variation in the wood that I had to tweak the back and side braces often during final assembly of the 70 box shelves. Even with good math and better tools and jigs than I had, this part I imagine would still be a fair amount of customization given the low grade materials I was using.
Attach angled braces:
I tried screwing in the wood screws here without pre-drilling but that didn't work so well. So I pre-drilled and then screwed to attach the angled braces. The purple in the image shows where the screws are going inside the wood. Only the heads are visible.
FYI, the back brace came from some scrap furring strip that was partially painted white.
Step 5: Drill Holes for Horizontal Stabilizer Bolts
Note: Are these screws or bolts? They're called machine screws but they come with nuts, which means bolts to me.
Step 6: Sand
Step 7: Assemble Multiple Box Shelves
Load them with your stuff. Get to everything instantly!