Custom trees floating

(2021.3)

my custom trees are floating, as shown in the screenshot at the bottom, ive looked over the forum and found nothing that could help me, most tutorials would send me to this tutorial --> https://www.youtube.com/watch?v=2ggSrLiXTuU&list=PLAeL-oIFIEngE6jRgFYeF…;

but it looks too hard for me because i dont understand the procedure thats shown (0:21) 

i used structures and other people have said is because its spawning on the air blocks and not the actual log even though ive set it to only spawn on grass, here is what my structure has inside it.

does anyone know a easy fix for this without having to use the complex stuff that is shown in that video?

thanks 

https://imgur.com/ZAzMTX9 <-- bad spawn

https://imgur.com/ZoOgblA <-- structure

https://imgur.com/QOhjvui <-- this is what the tree looks in the structure block thingy, the pastle boxes floating are the void boxes which the trees choose to spawn on and not the log it self