I dig a trench about 3 inches deep if that will accommodate the root ball or just enlarge the end where you are putting the root ball and lay the rest of the stem in the trench and cover with soil. Of course you can dig the trench deeper if you'd like but at least 3in deep. The top of the plant should not be covered, of course, and I prop up the top with a small nursery pot until it starts growing, usually a week or so. I got a great deal on a bull's heart which was pot bound in a tiny pot and so leggy and tall the stem could not support it, I planted it as I described and it is now healthy and has several beautiful tomatoes on it, not yet ripe. You do have to be careful where you dig after you plant a tomato this way and I water this tomato differently then my others, making sure I water over the whole stem area. I always mark the area with something to remind me where the stem is to I don't forget and dig a hole and ruin the tomato. Yeah, it is a good technique for the really tall and spindly tomatoes.

It might be leggy because it is trying to find the sun. Don't let the water stand in that tray. Avos don't like their feet wet.

Yeah I bought it from this Cactus nursery. The man had been growing cacti for over 40 years now. Apparently he uses such a complex mix, it has 9 different ingredients, I don't know why. Mostly it's river sand and different parts of Compost like goat and cow droppings etc etc. But yeah it's mostly a lot of river sand. Should I always wash off the small particles stuck onto the roots like that? I was scared of damaging the roots so I left what was really stuck onto the root hairs.

Why don't you just plant them out deeply. They'll take care of themselves. Putting the seed end three inches deep isn't going to harm anyone, and you end up with a functionally erect plant.