There are commercial alternatives to this table but they tend to be rather pricey. Making it yourself with save you some money and of course be much more fun. The project will probably take about 3 hours to complete. Maybe a little more if you have to work on the crates before they are presentable.
Step 1: Go Shopping
Before getting started you probably need to go shopping. This is what you need.
1. Four crates
2. Spare wood or one extra crate for material
3. Wood tint for the base. Try to match the color of the crates but it doesn't have to be perfect. The base will be underneath.
4. Mounting angles (see later steps)
5. Short furniture/bed legs