How to Build a Plywood Box for Modular DIY Storage

Modular boxes, more commonly known as shadow boxes, are an easy, affordable storage solution. Follow this tutorial to learn how to make them yourself.

Jessica Bennett

Updated on October 27, 2022

DIY Advice Modular Boxes — Photo: Jay Wilde

Working Time: 6 hours
Total Time: 12 hours
Skill Level: Beginner

Modular boxes, sometimes called shadow boxes, can satisfy a variety of storage needs, including a catchall in a child's bedroom or living room or a striking showcase for collectibles. Because they stack, you can easily move or rearrange them. Best of all, you can build seven 12-inch-square plywood boxes from a single 4x8-foot sheet.

Try painting the birch plywood box and adding ash veneer tape to the edges to give your modular boxes a distinctive look. For a more colorful accent, paint the entire box. Or you can accent the birch plywood with walnut plugs and veneer.

You'll likely need several hours to build and finish seven boxes. Before you begin, assemble materials and prepare your work area. Then follow these steps to learn how to make DIY modular boxes.

What You'll Need

Equipment / Tools

1 Measuring tape
1 Clamps
1 Electric drill/driver
1 1-1/2-inch spade bit
1 1/16-inch drill bit
1 Table saw or portable circular saw
1 40- to 60-tooth blade
1 Handsaw
1 Try square
1 Framing square
1 Hammer
1 Nail set
1 Putty knife
1 Foam paintbrush
1 Iron

Materials

1 3/4-inch thick, 4x8 foot sheet of plywood
1 Wood glue
8 4d finishing nails
1 Wood putty or filler
1 Sandpaper
1 Primer
1 Paint
1 Ash veneer tape
1 Walnut dowels, if desired

Instructions

Make Cuts

Cuts

Piece Dimensions Quantity

A sides 3/4" thick x 10 1/2" wide x 12" long 2

B top and bottom 3/4" thick x 12" wide x 12" long 2
Cut Tops and Bottoms

Use a table saw to cut the sheet of plywood according to the cut list above. For the tops and bottoms of the boxes, set the table saw fence to rip 12 inches wide. You can also use a portable circular saw and clamped straightedge for a guide.
Rip Wide Lengths

Rip two 12-inch-wide lengths from the 4x8 plywood sheet. Then rip two pieces 10-1/2 inches wide (or to your measurements) from the remaining stock.
Be sure to measure the exact thickness of your plywood before cutting the sides, as some plywood might be slightly smaller than its stated thickness. That inconsistency will throw off your measurements for the sides of these boxes, which are sawed to 10-1/2 inches wide to allow for joining to two thicknesses of 3/4-inch plywood at the top and bottom. So before cutting, measure the plywood's thickness, then deduct twice that from 12 inches for the width of the box sides.
Support Plywood

To support plywood during crosscutting, attach an auxiliary fence of 3/4-inch stock to the miter gauge with screws. Keep it about 1/8 inch from the fence to avoid binding.

To make sure that all the box pieces are square (if they're not, they won't fit together correctly), use a framing square to check the auxiliary fence before cutting. Use some scrap plywood to make a test cut. With the framing square, check the test piece. Adjust the setup if necessary.
Crosscut Lengths

Set the table saw blade and auxiliary fence to get a 12-inch-wide cut. Crosscut all the plywood lengths. You should end up with 14 pieces measuring 12x12 inches and 14 at 10-1/2x12 inches.
Make a Clamping Jig

It's easy to go astray when assembling so many units, so build a clamping jig to help with assembly. Use it to hold the four sides square to each other while gluing and clamping. You can clamp the jig in just one corner, because if one corner is square, the opposite one is also square. To make a clamping jig, first clamp together (don't glue) a box top (B), bottom (B), and two sides (A). Be sure to assemble the pieces correctly. Measure the inside of the clamped box.
Create Holes for Clamp Heads

Cut a scrap of 3/4-inch plywood to the box's inside dimensions, minus about 1 inch on each side. Bore 1-1/2-inch holes with a spade bit in a drill about 1 inch in from two adjacent edges. These holes will accommodate the clamp heads.
Clamp and Adjust

Assemble the top, bottom, and two sides with glue, then clamp the box, using the clamping jig to check for square. Make any needed adjustments before the glue dries.
Remove Clamps and Nail in Place

After the glue has dried, remove all the clamps and drive 4d finishing nails into the corners to reinforce the assembly. Be sure the nails enter the wood squarely. A finishing option: Use screws and plugs.
Fill Nail Holes

Drive the heads of all the finishing nails below the surface of the wood with a nail set. Fill the holes with wood putty or filler. When dry, sand them flush.
Fill Plywood Edges and Sand

Fill all plywood edges, except those at the front of the box, with wood putty or filler. Sand all filled edges smooth and lightly sand the box surfaces. Remove sanding dust with a tack cloth.
Prime and Paint Boxes

Apply a coat of primer to the box (except unfilled edges). Then sand lightly again. Touch up any blemishes, then paint on one or two finish coats of semigloss enamel.
Add Finishing Touches

Add ash veneer tape to the unfilled edges when the paint is dry. Miter-cut the corners of the tape. Accent boxes with walnut plugs, if desired. To install, join the pieces with screws in countersunk holes; plug the holes with walnut dowels for contrast. Then apply walnut instead of ash veneer tape and coat with a clear finish.