Gather your wood planks, and for each one attach a brace on one side, with 3 mircon screws for each brace to clamp them firmly onto the wood.

Starting from the bottom step, screw a small support starting from the middle hole of the brace to the rightmost hole in the step above it.

Directly parallel from this support, screw a large support from the leftmost hole of the bottom step through the middle of the second to the right of the third.

Repeat until all the steps have been properly screwed in.

Do the same for the opposite side.