This Bunk Using Full Solid Wood, and Slide use MDF Board which is 18mm thick.
For making Bunk bed Size of bed is important, European Mattress size never same as Asian Mattress size.
For that reason Side rail and Headboard size different. But making process is same
Here we added all the size of bed.
Wood sizes depends how strong bed frame you want to make. Bellow i write some sizes for you, it might helpful
Piller size 2" X2" wood
Side rail 1" X3" wood
Cover side rail 1" X2" wood
Staircase 1" X2" wood
Headboard 1" X2.5" wood
Slide for use 18mm thick Mdf board.
Some of clear picture might helpful for you
So i added bellow