ST stacking is a more-or-less sustainable (under Random Generator) method of stacking tetrominoes to form successive 4-line clears and T-spins. In Tetris DS standard mode, this stacking method achieves near maximum points per line. It's superficially similar to one of the T-spin triple setups but allegedly easier to learn.
First build this
Drop an S
Spin a T
T-spin double
Leaves one row of garbage
Build more layers
Another S and T
T-spin double
Leaves another identical row
After a few rows of garbage have accumulated, use I tetrominoes to break it down: