Assemble your detail pieces. Lay out your pattern by turning the remnant face down on the floor. Trace your pattern on the back with a good marker. Cut out the shapes with an exacto knife.
Lay out your pieces. Play around with the order, until you are fully satisfied.
Turn each piece over, so that your whole rug lay face down.
Run strips of carpet tape along the back of your remnants, to bind them together (duct tape also works, but it doesn't last as long).
Trim the edges. Add the detail pieces, and affix them as you did in Step 4.