How do I design a "swoosh" with my available plants??

I'm so tired of designing my garden with stripes, rectangles and squares. The Jordan shoes signature "swoosh" is like a smoothed out check mark and it fits my physical limitations: the plants are marigolds, which must be deadheaded so need to be within my reach (the edge of my garden).

Only how do I design it? I have 101 marigolds (started earlier from seed) and a garden area of 49" wide by 209" long. No way do I count on filling all that area with my few plants; I'll eventually get some more plants for the far, empty part. I'm thinking of making a "swoosh" in the bottom right corner (nearest my front door).

My garden helper will plant my plants for me but I must design where they should go. . so that I can care for them.

How do I figure this. . .design this. . .?? It doesn't seem right to use the formula for area of a triangle. . 1/2(b*h). . as I can't find planting density info for marigolds. . only spacing.

This math is beyond me!

HELP!!!