Lay out stiff plastic, metal or wood strips -- uncut -- in a crosshatched pattern. You can make this a Y-shaped trellis or a rectangular grid, but keep the overall design small. Mini-trellises tend to be less than 3 feet in height. Design Y-shaped mini-trellises with a long central stem that you can stick into soil, and rectangular grids with longer posts on each side.
Place small pieces of masking tape lightly around each intersection of the strips to keep the frame steady as you start to connect the pieces. The tape doesn’t need to be secure, it just needs to give light support.
Wrap gardening tape, plastic ties or duct tape around one intersection of strips at a time to secure the trellis together. After removing the masking tape, hold the two strips steady in the desired position and tightly wrap the intersection with the tape or ties. Repeat for each intersection, but stop after each one to make sure you like how it’s turning out. If you see a mistake, correct it before moving on.
Cut the excess ends of the strips so that the edges of the trellis are even. The material of the strip determines what cutting tool to use. For example, a small hacksaw would work for plastic. You can have some strips sticking up past the top horizontal strip, but make them as visually appealing as you can -- don’t leave different lengths sticking up in a disorganized pattern.