Step One: Find two 4 ft long sturdy sticks and two 12" sticks. These are the sizes I used, but you can make them bigger or smaller depending on where you want to put your trellis.
Step Three: Use twine to secure each intersection. Wrap a few times around one diagonal then switch to the other direction. Tie in a secure knot in the back of the trellis.
Step Four: Stick in your planter and place your vines accordingly. Looks like I'll need a bigger trellis soon.