No one can tell you
How Long it will take, because we don't know your proficiency level, only you know you carpentry skill level and tools available to you.
Do you have panel saw?
Like previously posted, I have the proper professional tools to make those, I have many years of carpentry experience, and could knock those out rather quickly. I have NO idea how long it would take YOU!
Oh, and I don't use nails, only exterior grade screws, so they hold up to transport and weather.
Good luck with your project.
