This was a function ornamental garden bed I wanted to make for herbs. It took about 2 hours, with help from another person. you can use anything for the spiral, from bricks, cobblestone as I have, or wood, to make any type of bed that fits your garden!
Step 1: Hugelculture
A simple technique which store long term nutrients and get the shape we want. Pile a lot of plant material, beginning with large logs, then to stick, then to organic matter. Finish with compost and dirt. I'd suggest placing a stone perimeter so you know where to build.
Step 2: Cobble
Place your cobble stone in a spiral all the way up. Alternatively, you could use logs or other materials like brick and unfinished stone. on the mound, make a sturdy place for each stone and spiral up to the top.
Step 3: Line Dirt (optional)
I would recommend using cardboard or organic sheeting to line the hugelculture mound with a barrier. This way, you fine, growing medium on top does not sprout weeds as quickly, and endures that only plants with dedicated planting positions can initially grow. One lined, place a fine dirt growing medium on top for your plants.
Step 4: Plant and Enjoy!
Now you've worked tirelessly to create a beautiful, interesting, and productive garden feature. Good luck and enjoy your new spiral Herb Garden.