UPDATE 11/24:
Just finished another pair - updated the info below with a few more specifics than before....
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I made my boots from leather zip-up ankle boots. I know they aren't exactly screen accurate (they're leather) But they ran me only about $25 each. I made two pair so you'll see two slightly different boots in the photos. I Started with a pair of black leather boots:
http://www.TK409.com/images/fett/boots/9.jpg
http://www.TK409.com/images/fett/boots/10.jpg
http://www.TK409.com/images/fett/boots/1.jpg
Painted them with gray latex house paint:
http://www.TK409.com/images/fett/boots/2.jpg
Then I weathered them with tempera paints (olive, black, and gray from a craft store). I used some very small black piping (fabric store) and trimmed off the extra fabric. I drew lines on my boots where I wanted the piping to go and added it to the boots using regular superglue:
http://www.TK409.com/images/fett/boots/11.jpg
http://www.TK409.com/images/fett/boots/3.jpg
I primered the soles with KILZ Latex sealer/primer house paint. Then I added two coats of white latex (not gloss) ceiling paint. For the spike mount, I used 1/2" wide X 1/8" thick aluminum flat bar (hardware store). I bent it in a vise (it's aluminum so it bends easily) Drilled holes for the screws, (first in the aluminum, then the sole) then I screwed the mount directly into the rubber sole of the boot:
http://www.TK409.com/images/fett/boots/4.jpg
http://www.TK409.com/images/fett/boots/5.jpg
For spikes, I used common pencil tips and glued them to the mount (used superglue gel). I also trimmed off the extra piping at the toe and sealed it with super glue to keep it from fraying:
http://www.TK409.com/images/fett/boots/6.jpg
Then I weathered the soles with the tempera paints:
http://www.TK409.com/images/fett/boots/11.jpg
http://www.TK409.com/images/fett/boots/12.jpg
http://www.TK409.com/images/fett/boots/13.jpg
http://www.TK409.com/images/fett/boots/14.jpg
http://www.TK409.com/images/fett/boots/7.jpg
http://www.TK409.com/images/fett/boots/8.jpg