@pale_blue_is
Raising bonsai from seed is the "slow route" to bonsai success. The first 5 to 10 years of raising bonsai from seed is the "nurseryman's phase" of bonsai. The techniques are mostly just plain old nursery style horticulture, with very few "bonsai techniques" applied. Most exhibition quality bonsai spend a decade or more being grown to a size 5 to 10 times larger than their finished bonsai size. If you tour a bonsai exhibit, the pine or flowering apricot that is about 18 inches tall (roughly half meter) most likely spent 5 or more years being 15 feet (roughly 5 meters) tall. Bonsai from seed are first grown up and out to develop the trunk diameter. Then once the caliper of the trunk is sufficient for the image one wants to create, the tree is reduced in size until it has achieved the desired image. The large diameter trunk is needed to force perspective for the viewer of the bonsai. Slender trunks the diameter of a pencil or less do not visually create the visual impact of a large old tree in miniature. So the technique is to develop a trunk first, then reduce the size of the tree to the desired size of the finished bonsai.
If you are serious about learning bonsai, please read this thread. There is some good advice. In particular, first learning the horticulture of the species you would like to work with. Then acquiring a collect of trees in different phases of bonsai development. Don't just have young seedlings. Have a collection that includes seedlings, a few trees from nursery stock, and a few collected trees, whether collected from urban landscapes or from the wild. Also a tree or two that have been developed bonsai, and are already exhibit quality, as these mature developed bonsai will teach you the greatest number of bonsai techniques. There are techniques used only for exhibition quality trees that would never be used on younger material. So if you want to learn bonsai, you need a range of material in all phases of development.
Also network with local bonsai hobbyists and artists. Seeing the techniques done, live and in person, is an experience that You Tube simply can not compete with.
After reading a lot of beginner threads on this site over the years, I am going to create a thread of advice about how to get the best start on your bonsai journey. Simply put - take advantage of all of the people who have gone before you! At some level there is a bit of skeptic in all of us...
www.bonsainut.com