I use a seed starting soil, its very fine and has low nutrition for better root growth from the start. When they look like this i start separating them and add nutritious soil. Warmth might be the most important factor, i think.

I also have a grow light, this helps me with water control because the soil dries out more quick, so overwatering is not a big problem for me. hope this helps :)

What kind of beans? 🫘 Will set up a patch for carrots too! I want to try to not dig and instead putting cartons and compost layer on top 🥕