Seeds are available from hydroponic retail stores as well as many mail-order seed companies. Sow lettuce seeds into 1-inch cubes and don't transplant them into blocks. Sow cucumber seeds directly into 3-inch blocks. Immediately upon germination, place the seedlings under light. Transplant herbs at a similar stage, but note that the time until true leaves appear may be considerably longer.
European cucumbers take two to three weeks, and peppers take five to six weeks.
Transplant tomatoes into 3-inch rock wool cubes after the first true leaves unfold, in about two weeks. When transplanting, be careful not to damage the tender roots underneath the blocks or cubes as you set them into the holes in the growing channels. The easiest way to support vine crops like cucumbers and tomatoes is to tie their stems to polyethylene string running from a support bar attached to ceiling hooks or from a support frame. Place hinged plastic stem clips under a strong leaf stem every foot or so along the plant's main stem. The clamp's hinge pinches the string when the clamp is closed.