Another method of growing carrots from seed or other things is to buy a length of plastic roof guttering. Pour in seed compost and sow. When sprouting dig a trench and slide in the seedlings.
I have tried this, didn't find it particularly successful. The first problem was it wouldn't slide and bunched up, reducing the length of guttering helped, but then I found that the carrots were not making it past the join between the seed compost and the ground and grew small and twisted in the top couple of inches. Mind you my soil is heavy clay, and I have never really had success with carrots in it, it might work better with loamy soil.
I am fully converted to the idea of carrots in containers, I can give them soil they love, carrot fly and other pests have trouble finding them, and I can lift them up and sit down comfortably to do those jobs like thinning and weeding that usually take so much bending. Also I can do them any time of day, not wait 'til evening, as I can leave them on the table and they are unfindable to carrot fly.