I grow my Parsley in 8-10 inch pots. Just use garden soil to topup the previous pot soil and mix it all up with a little fresh seed compost before sowing new seed.
I sow the seed in a succession of pots from February to about now and leave indoors near a window, until the seedlings get to about an inch high.
I then move the pots slowly outside to acclimatise. They never really seem to mind the jump.
I have all my pots placed at the foot of a fence, so could say is semi-shade depending on the time of day.
Do water the pots a few times a week if its not rained.
Parsley does take a good 14 or more days to germinate. But once up, grows quick.
I always grow flat and curly seeds in separate pots and they always both come up the same.
The way I grow it I am picking Parsley from the pots the first year and second year before it eventually starts going to seed in the second year Autumn. I always keep one of each pot variety and move them to a darker part of the garden to flower the next spring and collect the shake off the seed.
Have over the years tried transplanting small seedlings, but find they do not grow into good plants.
Regular cutting is the key to Parsley, do not be afraid, the more you cut the more your get.
Do sow carefully too, try and space the seeds a good 1/2inch apart. The seeds are small but it is worth taking the effort, otherwise you are wasting seed and crowding the seedlings. The seedlings when small are not easy to pick out without disturbing the others..