This method is reliable and cheap, but it is not the only method. People who grow lots of sweet potatoes often prefer to start them in shallow beds in the ground. There are quite a few YouTube videos which explain this process in detail. I grow my sweet potatoes mostly for home use. They are not an ideal product to sell at the farmers market. They take up a good bit space in the garden and have a lengthy date to maturity. However, they tolerate poor soils and can sooth a green thumb in late winter.
The second plant which I intend to start indoors this weekend is garlic. I have never grown garlic, but similar to sweet potatoes, I am looking to sooth my green thumb while also growing some for personal use. It is best to start garlic in the fall. However, it can be started in late winter for a smaller harvest. Garlic, unlike sweet potatoes, has some potential as a product for the farmers market. It can be grown effectively in dense spaces. Garlic does have a long date to maturity.