Use our template (find it at familyfunmag.com) to cut a 9-by 13-inch cake into the boot pieces, then assemble them on a serving platter.
Warm caramel candies in the microwave for a few seconds to soften them. Flatten one into a 1-by 3-inch strip for the boot loop. Knead together the remaining caramels and roll the candy into a 14-inch-long rope. Flatten the rope into a 3/4-inch-wide strip. Knead together red gumdrops. Sprinkle your work surface with red sugar sprinkles and roll out the gumdrops into a 1/8-inch-thick piece. Repeat the kneading and rolling steps with yellow gumdrops and yellow sugar sprinkles. Use our templates (find them at familyfunmag.com) to cut out the boot strap hardware, spur, and decorative embellishments.
Score the cake with a toothpick to indicate where each frosting color will go. Frost the cake, using the milk chocolate for the sole and heel. Spoon the remaining chocolate frosting into two separate ziplock bags. Snip a corner from each bag, then use the dark chocolate frosting to pipe on the stitching and color outlines and the milk chocolate to pipe a wood pattern onto the heel.
Press mini chocolate chips, tips down, into the foot of the boot. Arrange the prepared candy pieces, trimming any excess as needed. Add red and brown M&M's rivets as a finishing touch.