I started by laying out the cut lines.

Then, I cut the plywood to size.

Next I measured and marked the 2x3s for the 4 long sides of the platforms.

Then I cut the 2x3s to length.

Then, I marked the short sides and cut those out. I needed 6 of these (2 will be for center supports).

I then cut the 6 short pieces to length. 

Next, I cut out the small strips for the tops of the platform. These will be “grips” for the dog. 

This is an image of all the wooden pieces cut out for this project.

Next, and before starting to assemble the platforms, I gave every pieces 2 coats of paint/primer. This doesn't have to be pretty because I will be painting it with different colors later, but this just gives the project a little bit more weather resistance since I plan to keep it outside during the summer. 

Once the paint/primer was dry, I started to assemble all the pieces using glue and screws.

And once the "frame" was assembled, I could apply the top to it.

Again, I used glue and screws for this step. But before installing the screws, I pre-drilled the holes with a counter-sink drill bit. This way the screws sat flush with the wood surface and the dog wouldn't hurt their paws. 

Next, I marked out and attached all the "grip slats" to the tops of the boards using glue and brad nails.

With the "grip slats" installed, I could attach the two halves together with a pair of hinges.

I tested it out and it seemed to work just fine.

Next it was time to install the screw eyes to the platforms. These are the anchor points that the chain will be attached to and allow the a-frame to be angled at different heights. I later moved these to the inside face of the 2x3s (see image below).

With the screw eyes attached, I could link the chain between them on both sides using spring links.

With this project just about wrapped up, I gave it a two-tone paint job. I read somewhere (not sure if it's completely true or not) that the two-tones of paint help the dog recognize that it's a ramp and not just a flat plane in front of them.

And finally, I added a handle to the side - although I found it easier to just bear-hug it and move it around... or ask a friend to help you lol.

Now all that's left to do it use it!...or rather, have your dog use it!