Seed balls will work, but you might need to make them larger to have enough soil above the wood chips. The seeds germinate in the seed ball soil and roots go down to find the soil under the wood chips. Need consistant moisture to germinate, so the balls allow this. Fukuoka is seeding into straw/clover on top of soil so any size balls will work.
In the picture, he has compost or some soil medium on top of cardboard, which would work if you add compost or top soil on top of wood chips and seed into it.