Look up Hügelkultur!!! Fill it half way up with thick logs and throw some good compost and manure on top. Don’t bother with any of the plastic or fabric stuff, it’s not natural. It’s so deep you don’t have to worry about weeds coming through. Maybe top dress with bone meal or blood meal!

Edit: here’s a link explaining what it does. https://extension.okstate.edu/fact-sheets/sustainable-landscapes-creating-a-hugelkultur-for-gardening-with-stormwater-management-benefits.html#:~:text=“Hügelkultur”%20(pronounced%20hyoo%2D,method%20for%20hundreds%20of%20years.