You need to measure the inner edge of the crate before it cut, screw the sideboards and the bottom. You can repeat the process to make the bottom side, or cover if you want.
The crates will look much impressive if you color it. The process is quick and simple and detailed below. If you are searching online for timber crates then you can take a look here https://www.craigtimber.com.au/timber.html.
First, select the area of work and cover the floor with cloth for protection. Use a brush to apply the color, and be sure to stroke in the direction of the box. Keep a wet edge at many times, and apply as much as wood colors will take.
Once you have colored all over the crate, wait for about half an hour. When the time is up, run a dry brush on the box to remove excess stain. Penetrates colors will not dry hard, but any colors that are not absorbed may be sticky and can be pulled by something that comes in contact with the crate.
This is a procedure for a basic wooden crate. Depending on the end-use, you might want to make it up a little bit more. You can use paint instead of color wash, adhere decorative items out of the crate, or an artist paint pictures on them.