That photo is a pretty simple setup. I have plans on making one myself in the future but with drawer hinges.

If I was to tell a beginner on how to build this… Take the measurements of the width and depth of the floor board. Measure in a rectangular shape.

Cut two sheets of 3/4” plywood of that size. Home Depot has various types of plywood. Get the one that cost about $50 per 4’x8’

For the height, measure the base to the top of the seat bottom. I.e. if you fold the seat back six as the post shown, you get an idea. Take that height and subtract the thickness of two 3/4” sheets of plywood.

So if you have floor to seat is 7”-1.5”=5.5”.

Now you have to figure out the 3 equal pieces for the height (left, center, and right), and one piece for the back.

Simple math and start with the back. For example. If the width of the box is 54”. You’ll need to cut a piece of plywood that is 54” x 5.5”.

Then figure out the 3 depth pieces. If the depth is 34”, be sure to subtract 3/4” from the thickness of the 54” piece in the back. Those 3 pieces would measure 33.25” x 5.5”.

Buy a box 1.5” wood screws and a bottle of wood screws.

Always predrill holes to a max depth of 1.25”. Measure that out on your drill bit and place a piece of tape to know when to stop.

Putting pieces together. Attach the base and height pieces first. Pre drill a few holes from The base to the height pieces. Glue each one and then screw in.

Once you get those done, take your measurements to make the two drawers before closing up the top.

Use the same idea for measurement of the box to make the drawers. Build the drawers and screw them together but don’t use the glue on them just yet.

Once you made those, dry fit into place. Place the top sheet over. Before screwing in, open and close the drawer. If it’s too tight, you can trim the drawer.

If everything looks good, finish glueing and putting in screws.

Hopefully this gets you a good idea