For my garage entrance I'm going to build a two foot by three foot platform.
To start, build a simple box of two by sixes. I had mine cut to size at the lumber yard.
I am also using pressure treated lumber and decking screws that won't rust.
Once the box is assembled, check to make sure it's square by measuring from corner to corner in both directions. The measurements should match.
Next, assemble a second box inside the first to act as support for both the outer box and the step's tread. Secure the inside box to the outside with screws.
Next, you need cross supports for the top tread. For a two by three box, place two cross pieces 12 inches apart. Again, secure it from the outside of the box.
Once the framing is assembled, you're ready to build the top.
For a finished look, I want to build a frame for the outer edge, kind of like a picture frame. To do this, cut inch and a quarter decking boards with 45 degree angles at each end.
Secure your frame to the top of the box with more screws, making sure that your corners are tight.
Once the frame is secured, you want to fill the center portion of the frame with more decking.
And there you have it, a solid finished platform step for your garage.