As you can see, it's pretty cool, but Billy's building instructions did not work so well - he'd improved the design, updated the files, but left the build instructions as they were. That made things a little confusing, so I decided to write some myself.
Step 1: Files & Glue
You can start by downloading the SVG or DXF file from Thingiverse, or you can use the ECP file I made for my own laser cutter (on this step). The only difference between Billy's files and my own is that I set the cutting order to drop out the scraps first, and added a small plaque to stand with the finished model.
It is scale to work with 3mm thick material - I used poplar plywood, MDF would also work well.
Since I used plywood, I used glue to fix the parts together.
Step 2: Start With the Body.
The body is a simple box, but you need to be careful about which way round you fix the parts - the etching on the side will guide how you fit the legs later.
You also need to make sure that the cross-shaped hole is at the right end, for fitting the neck & head.
Step 3: Roof and Neck
Set the body aside - as it dries, you can put together the cabin roof and the neck.
Be careful not to glue the disc with the cross-shaped hole into the roof, and it forms one end of the neck.
The neck parts slot & glue together, then the disc glues on the end furthest from the wide section.
Step 4: The Hips
Look for the six small oval-ish parts.
They glue together to make two spacers - pay attention to the slight bulge on one end when you are lining them up.
Step 5: Legs, Part One
Find the parts laid out in the first image.
Turn the bird-shaped parts over, then glue the longer part on top at the circular part - there are two etched lines to help you line them up.
Set the glued parts aside to dry.
Step 6: Legs, Part Two
Another find-the-parts-and-glue-them step.
Use the etched lines and small holes to line up and glue them.
Note that the longer parts have been turned over between the first and second photos.
Again, set them aside to dry.
Step 7: Legs, Part Three
The sections you constructed in the previous two steps now get glued together.
You should end up with the bird-shaped parts, and the shorter parts, sandwiched between two longer parts.
Step 8: Legs, Meet Hips
The bird-shaped section at the top of the legs has an engraved shape.
The non-bulged end of the hips glues to this shape. This is one of the joints that will bear the weight of the finished model, so you should clamp it while it dries.
Step 9: Feet
While the legs and hips are drying, you can build the feet.
The construction is obvious, but be aware that the arched pieces come in two slightly different sizes - the smaller ones come closer to the toes.
Step 10: Chin Gun
While the other parts are drying, it's an ideal time to build the armaments.
The chin gun is made of three parts that glue in quite an obvious manner.
Step 11: Right-cheek Weapon Pod
The gun that will end up on the right "cheek" of the walker is made of three layers glued together.
The etched lines show you how to line them up.
Step 12: Left-cheek Gun
The left-cheek gun is more complex, made of five parts.
The two etched gun-barrels get layered together (the short one gets turned over and glues underneath).
The other parts slide on on order - do a dry run before you glue to make sure that the gun-barrels finish flush with the squarish section.
Step 13: The Head
The head is a little awkward to glue, because none of the angles are at ninety degrees. It's practically impossible to clamp traditionally.
Glue the "cheeks", roof and front together first. Hold them together long enough for the glue to hold itself firmly.
Before you add the back, the "eyelids" get slotted in from the inside.
Once the first four parts have dried, glue on the back. Again, because of the odd angles, you'll need plenty of glue. You can, though, clamp it this time, at the bottom.
Step 14: Add the Feet
The ankle part of the leg has lines etched on it to line up the feet.
Like the hips, the ankles will be taking the weight of the model at an odd angle, so clamp them while they dry.
Step 15: Adding the Armaments to the Head
While the feet dry, you can finish the head.
The left-cheek weapon pod slots and glues into the small square hole on the left side of the head.
The right-cheek gun glues to the area marked on the left cheek.
The chin gun glues into the chin. It's a very close fit, but you might see a very thin gap towards the front of the chin - you may need to use a scrap of paper to "shim" the joint. I didn't, but you might.
I also glued on the roof hatch that I forgot to glue on in step three.
Step 16: Add the Legs to the Body
The body has marks on it for lining up the legs.
It is easiest to add the legs one at a time, clamping the while they dry.
For the second leg, I glued it, stood the body up, made sure the feet met the floor properly, and then clamped it.
Step 17: Final Assembly
Now is the time to put everything together.
The neck glues into the cross-shaped hole on the neck, and then the top circle sits in the circular socket inside the roof of the head.
You'll notice I'm holding the body in the first two photos - the walker won't balance until it has the weight of the head in place.
Step 18: Posing
That's it, really - all you need to do now is decide how you want your walker to stand - turn the head, just so and work that camera!
The balance of the walker is quite fine - it will stand on a hard surface, but not on a soft surface like the fabric I used as a background in these shots - that was easily solved with a small cork coaster.
I made a small plaque to go with my walker as well, crediting Billy as the original designer of the model.
If you make one, post a photo in the comments, or, even better, pop over to Billy's original posting and leave a comment or image there, and show your appreciation for the efforts he put into creating this model, and sharing it for us to enjoy.