I found a circular form with a similar radius to the deck extension curve. I soaked the quarter-inch stock in a thermos of water, then pressed it around the form, securing it with wide rubber bands and tape.
The wall is three inches tall, so that’s 12 lengths of quarter-inch stock.
Here are the first four courses.
And the subsequent ones. One of the boards cracked at the curve, so I need to soak and form the final course… tomorrow. The rest of the wall is a great opportunity to utilize the many lengths of quarter-inch siding I have piling up on my table.
I wonder if an actual woodworker cringes at the imprecision of my efforts as much as I as do, say, when encountering bad typography.