Joufuku is the size of paper used for hanging scrolls, etc. The size is Width: 34.5cm, Height: 136cm. Strictly speaking, it refers to the size of the paper, but it is sometimes used to refer to a category, such as "I want to write joufuku!" Generally speaking, it means writing about 14-16 characters on a large piece of paper.
The difficulty with Joufuku is that it is too large to write on a desk, so you have to draw a pad on the floor and crawl on the ground to write. This makes it difficult to reproduce the usual brushstrokes. Also, the large size of the paper makes it difficult to balance the position of the letters. Once you get used to it, you'll be able to write in a good position naturally, but until you get used to it, you'll have to fold the paper and write in other ways.
Everyone has their own way of sitting, but it is generally said that it is best to write on all fours without touching your butt. However, it's very difficult until you get used to it, so I think it's best to just sit down and write freely. It's good if you can concentrate and produce good work.