I'm in soil, but LST is pretty much the same.
You just need to figure out how to fabricate tie downs in your space. - anchors, edges of pots, etc. try to keep a minimum of mess down low
I didn't succeed, but I tried --- I had pipe cleaners everywhere (but the white stand out nicely).
Use a thick, soft wire or store bought products to tie your plants as desired.
I used the soil / edge of the pots as anchors and pipe cleaners as my tie downs.
I'm new - pipe cleaners are weak, and I bent a bit of spring action into them so that branches I had been too aggressive with would have a chance to flex the spring / pull the anchors from the soil. --- That saved me a couple times.
Next grow the training wheels are off - I'm using thick coated solid core electrical wire (because it's in my tool box).