The current dye trend isn’t so much “tie dye,” which is a method that became emblematically popular in the 60s and 70s. (You can learn to tie-dye here.) Today’s dyed pieces are created using an ancient Japanese technique called Shibori, which is a process in which fabric is bound, folded, stitched, twisted, wrapped and/or compressed. Traditional Shibori uses only indigo as a dye, but you can use any dye available to create the same patterns with a brighter palette.
Place the folded shirt between the two boards, leaving about an inch of the folded edges hanging out of the boards. Wrap the rubber bands as tightly as possible around the boards, to compress the whole thing like a sandwich. This will keep the dye only on the exposed edges of the shirt that were outside of the boards.
Prepare a dye bath of a few teaspoons of fabric dye to a quart of very hot water in a shallow dish. Place the exposed fabric in the dye bath, resting on the bottom of the container. The whole package should balance nicely upright — exposed t-shirt edges in the bath, with the rest of the package upright out of the dye bath. Soak for about five to seven minutes.