For beginners who find starting seedlings a problem, check the website below.
Here is a link that might be useful: Hydroponics Notebook
That is a very concise, very well illustrated description.
One warning, as soon as seedlings emerge they must get adequate light or they will become leggy and not have strong stems.
Lettuce seeds should be sowed on the surface of the media. I also recommend a small pump-type sprayer bottle to mist the seedlings a couple of times a day until germination.
Thank you for your suggestions. I think they are very important. I will revise the text in the website. Is it alright if I incorporate your suggestions?
Your suggestions have been incorporated in my website.