Hi, and welcome!
With carrots, the aim is to give them a nice clean root run, as this is obviously the edible bit, and in order to grow nice and straight(ish) without forking the tap root must not become hindered by anything. By either buying plug plants, or sowing carrot seed in trays and then planting out, the roots will be hitting the bottom of the trays really soon after germination.
Carrots need to be sown in situ where they are to grow really, and you would need hundreds of loo rolls and lots of compost to make up the numbers of just one row sown direct.
Totty