You should do the same. Professional flats drain properly, make efficient use of space, and have cells that are formed to create strong transplants. If you're looking for good flats, we strongly recommend the systems found in the Propagation Supplies section of our website. Use a soil mix designed for starting seeds. It took us a long time to develop a soil mix that worked to our satisfaction.
Poor mixes yield poor results.
A good seed starting mix holds moisture, drains well, and is fine-textured. The latter is important because large particles in a seed starting mix will suppress seed germination. On the other hand, a seed mix that is made exclusively of fine materials will clog and drain poorly which causes seeds to rot. We offer bags of the mix we use in our greenhouse in the Propagation Supplies section of our website. Select a location with as much light as possible.