That size sounds fine. For the lettuce you can even sow the seeds in a nursery flat--they're pretty forgiving at transplant. Lettuce seeds are very small, and I found the flats an easier way to start seeds.

Yes I think the lettuce you can just plant a bunch and eat them when they're small. Brocolli would need much more time and lighting and isn't really practical to grow indoors although it's possible.

Lettuce:
Sometimes I had trouble with lettuce (direct sowing) until I learned that they need light to germinate. Last year (2014) I started them in a cell tray (small 1" x 1" cells) just putting the seeds on the surface of the seed starting soil and making sure they were moist in the sunlight for several days. Germination was great and they transplanted well. I had total success (way too much).

Broccoli:
I do start broccoli indoors and I have had good success. As I recall, I use the trays with 18 cells (3 cells x 6cells) - larger cells as the plants are larger. I do use grow lights and I harden off as early as possible.

I never ever raise lettuce seedlings I sow it direct in rows and then start picking once big enough until I have the right spacing. But I save my own lettuce seeds so I have enough to do that.

I leave the old lettuce plants in place. Once the seedlings emerge, I keep an eye on them, making sure that they stay watered. then I move them when they are big enough, and of course, pull out the old lettuce plant. Could it be any easier than that?

hello frds
I m babra n new here and a new gardener as well. I think I might. ..not might sure find help here. I m growing Chinese cabbage. it was going all well but now its leaves are turning yellow....I think something went wrong don't know what.
Some basic info is that growing my veggies on rooftop. Trying to attach pic as well. plz guide me I don't want my cabbage to go all wrong.
and do ignore my bad English n thx :)

There are some chinese cabbages which are very easily grown directly and I sow always way too much. They are called bok choi and similar names.
If you don't mind the ugly crates, in Australia greengrocers still have these white polystyrene cases they are ideal for growing seedlings, some people even grow veggies in them.

I got a tip that my 14 watt bulb can grow microgreens. It's a special kind though. Transplanting it then it would need more light probably. I don't think brocolii would mind a really big pot. The plants and the root sizes are often about the same with plants in general- not always I guess.