This depends on the type of wood and how evenly distributed both the load and the supports for the piece of wood are.
That will depend on how thick a layer you want.
thick grain or seeds
Ripsaw
cilia
Romanesque churches had thick walls to support the weight of the heavy stone ceilings and vaults. The thick walls provided stability and allowed for the construction of tall and monumental structures characteristic of Romanesque architecture. Additionally, the walls served a defensive purpose during tumultuous times in Europe, offering protection against attacks.
Even if the material is the same, the thick lens is stronger because strength increases when thickness increases. If you pull on the lens in its plane and it is twice as thick then it is twice as strong. If you push on the lens perpendicular to it and it is twice as thick then it is eight times stronger. This is strength of materials theory taken in college for engineering.
structural support
depends what its made of
XYLEM
An individual grain is usually a millimetre or less. A beach of sand might be metres deep, or just a few millimetres.
vitreous humor
Depends most plates laid down in the roadway are 2 inches thick to support most traffic.