It takes time to put together these resources like finding sand, making compost and leaf piles, but this is part of making your garden or farm complete. When these aspects of your garden are in place, you will also will be more complete as a gardener with the work you are doing. making potting soil puts you more in control, more informed about your work and a better facilitator of the land you are working. Remember that the garden and gardener grow together. There is more detailed information in my book, Radical Regenerative Gardening and Farming.
Place the ingredients onto a flat surface like a piece of plywood. It is
best to mix with a flat shovel. Get someone to spray a five mist of water while you are mixing. This allows air and water to go into the mix at the same time. You only want to moisten the mix, not saturate it, so it holds together well. If you can squeeze out a drop or two of water that is ideal. The mix I use is about 1 to 2 parts compost to one part sand and one part leaf mold. The standard recipe is equal parts compost, sand and leaf mold. This mix is best for propagating. Once the mix is made keep it damp so it stays rich and alive. This mix holds water well yet drains well. This means it is a balance of both properties. The photos below show the planters I use for small seedlings like spinach and broccoli. The box is made form old recycled crates. I place hardwood leaves in the bottom to provide air and so the roots don't stick to the wood. The picture on the right is the flat ready to plant. Tamp is down the whole box and scrape the soil level. Spay it lightly for small seeds.