
With just some basic wood working skills, you can build a simple backyard sandbox such as this one. This sandbox has colorful stripes, and has benches at the corners for sitting, has beach umbrella stand.

If you are far from beach, this sandbox is going to be a lot of fun for kids. Check out the plan and step by step instructions from Dana made it in the following link.
Dana made it – Backyard sandbox tutorial
You can also make a cover/bench as it is nicely done here.