Get a piece of plywood about 1 cm or half an inch thick. Saw it according to this plan

Please note that all dimensions can easily be scaled down or changed to fit your particular needs or the plywood you have available.

Also note the 45 degree bevel on the bottom edge of the front panel. It makes a nice fit to the bottom panel but if you can't saw at an angle you can just ignore it

Hold or clamp the back panel to one of the side panels and predrill & counter-sink the screw holes. Do the same with the bottom and front panels and temporarily screw them all to the side panel. Repeat this procedure with the other side panel.

Remove the screws, apply some glue between all the panel joints, put everything back together and screw down tightly. Wipe away any excess glue and let it all dry for a couple of hours.

Optional: glue & screw three 10 x 1 cm strips to the bottom of the bin to make it stackable.

Sand down the edges to a chamfer and smooth the panels. Add a coat of paint and/or varnish as you prefer.