Best way of Planting seedlings?

Hi , When planting a seedling, I first dig a hole. The topsoil at my site is only about less than 3 cm deep, while the seedling's root system is approximately 8 cm long. In this situation, would it be beneficial to place the soil from the bottom of the hole on the surface and the topsoil at the bottom so that the roots are initially surrounded by the more fertile soil? Or is it still better to keep the soil layers in their original order? What are the scientific reasons behind the recommended approach?
Im in the amazon jungle.

Cheers

R.

Keep the layers in order honestly. The topsoil has microbial life and organic matter that feeds the roots as they grow out, and flipping it buries that activity where it can go anaerobic. With only 3cm of topsoil though, I would focus on building it up over time rather than rearranging what little you have. Mulch around your seedlings after planting and let the worms do the mixing for you. Over a season or two the topsoil layer gets noticeably deeper on its own.