How did this guy build seapickles and frames on top of trapdoors? Is this a mod? How do I do it? He only mentions shaderpacks/texturepacks at the end of the youtube vid, no mods
Screenshot from around 25 mins in
Trapdoors can be placed flush with normal blocks, either at the bottom, or the top of the block, like so:
This makes it an "applicable" surface to place items on. This video shows how to make Iron Trapdoor Shelves, and shows that items can be placed on trapdoors at the appropriate height.
The only issue is that Wooden Trapdoors can be opened/closed with a right-click, whereas the Iron Trapdoors need a redstone signal, so placing items on an Iron Trapdoor is just a straightforward right-click. However, you can place items on Wooden Trapdoors, by holding L-Shift when you place the item.