How To Make A Toy Box

Rout or cut a 1/2" deep by 5/16" wide groove in one edge of each front, back and side frame stile (D).
Rout or cut a 1/2" deep by 5/16" wide groove in one edge of each side frame rail (C). Rout or cut a 1/2" deep by 5/16" wide stopped groove in one edge of each front frame and back frame rail (A). You should only make the groove in four of the five 2x4x40" rails. The fifth one is the backrest top rail and doesn’t need a groove. The grooves in the rails should stop just short of either end of the rail so they aren’t visible from outside the toy box (see Figure 4).

Figure 4 - Stopped grove in rail

Figure 5 - Stile receiving end panel

Lay out the pieces for the front and back panels. Mark the rails (see Figure 5) and cut mortises to receive the stile tenons.
Dry fit the front and back frames with the lauan panels in place. Trim any of the parts as needed.
Glue and clamp the front and back frames with the panels in place.
Lay out the pieces for the side panels. Mark the rails and cut mortises to receive the stile tenons.
Dry fit the side frames with the lauan panels in place. Trim any of the parts as needed.
Glue and clamp the side frames with the panels in place.
Rout or cut a 7/8" wide by 1/2" deep groove on the inside face of the bottom rail of each front and back frame. The groove should be 1" up from the bottom edge of the rail andstop just short of the end so it’s not visible from outside the toy box.
Rout or cut a 7/8" wide by 1/2" deep groove on the inside face of the bottom rail of each side frame. The groove should be 1" up from the bottom edge of the rail and extend the full length of the rail.

Figure 6 - Rail marked for mortise

Figure 7 - Side frame butted to back frame

Butt the back edges of one side frame to the inside face of the back frame. The outside face of the side frame should be flush with the end of the back frame. Counter sink screws through the back frame into the side frame to secure it in place. Secure the second side frame to the opposite end of the back frame.
Trim the floor piece from step 2 to 14 7/8 x 37 7/8" and slide it into the groove in the bottom of the assembly.
Dry fit the front panel to the assembly. You should be able to move the floor slightly with all the frames in place. Trim the floor if needed and secure the front frame as you did the back.

Assemble the Backrest:

toy box backrest stile aligned with back frame

Figure 8 - Backrest stile aligned with back frame

Align one of the backrest stiles with the outside edge of the back frame. The end of the frame should be flush with the edge of the stile and the bottom of the frame should be 1/8" below the bottom end of the stile.
Clamp the stiles in place. Use the backrest cross rail to lay out the mortise on each stile. Position the backrest cross rail so it extends 1" above the top rail on the back frame. Cut the mortises in the backrest stiles.
Dry fit the backrest cross rail and stiles and align the assembly with the back of the box assembly. The top of the backrest cross rail should extend 1" above the top rail on the back frame. Trim the pieces as needed. Glue and clamp the backrest assembly.
Position the backrest assembly on the back of the box assembly and fasten with screws. Screw through the box assembly into the cross rail and stiles so the screws aren’t visible from outside the box.
Lay the backrest top rail across the tops of the backrest stiles and mark the rail for mortises to receive the stile tenons. Mark the bottom edge of the top rail at the inside edge of each backrest stile and label the marks 1 and 2. Cut the mortises in the top rail.
Place a tape measure along the bottom edge of the top rail starting at mark 1 and ending at mark 2, you should have a total of 33" between the marks. Mark the center of the rail edge at 2quot; intervals, starting 1 1/2" from mark 1. You should have a total of 16 marks between marks 1 and 2. Transfer the marks to the top of the backrest cross rail.
Drill 1/2" diameter by 5/8" deep holes at each mark on each rail.

Figure 9 - Backrest assembly attached to toy box assembly

Dry fit the backrest top rail over the stile tenons. Make any adjustments needed. Measure the distance from the top edge of the backrest cross rail to the bottom edge of the backrest top rail. Cut 16 dowel rods 1" longer than this distance.
Insert the dowel rods into the cross rail and dry fit the top rail over the stiles and dowel rods. Trim the pieces as needed. Glue and clamp the top rail in place. Glue only the top rail at the mortise and tenon joints. The dowels should be free-floating.

Install the Lid:

Figure 10 - Lid support rail placement

Figure 11 - Friction lid support installed

Figure 9 - 1x6x42" piece with 6° bevel

Rip the 1x6x42" piece (I) to 3 1/2" wide. When ripping the piece, adjust the saw to put a 6° bevel on the board’s edge so the longest face is 3 1/2". Use 8d finish nails to secure the piece, centered left to right and butted against the face of the backrest cross rail.
Trim the lid support rail (J) to fit between the side panels and install it with wood screws as shown in the graphic.
Trim the lid piece you made in step 1 so it extends 1" past the front of the toy box. Use a router or sander to round over the outside edges of the lid. Align the lid with the 3 1/2" wide piece and install the hinges. Open the lid and install the friction lid support.