You can just buy a normal 2x4 framing stud which is 8' long, the actual dimensions of the 2x4 are 1 1/2 by 3 1/2.
You cut the stud into 2 24" boards, and 4 12" boards
then you face nail the 24"er flush with one of the 12"ers and you have a 2 board (3" thick)
then nail the other 24"er to two 12"ers and you have a three board (4 1/2" thick)
the leftover can be your 1 board.