1. Soak two bricks of florist's foam in water for 30 minutes. While they're soaking, cut the flower stems and let them stand in a bucket of water mixed with floral food.
2. Cut both bricks to fit the plastic liner with 1 inch extending above the rim. Secure the foam to the liner by wrapping them together with florist's tape.
3. Cut the dry brick of florist's foam in half lengthwise. Place it in the bottom of the basket. Set the liner on top of it; the rim of the liner should be almost level with the basket rim. Add floral food to a quart of water, then fill the liner. Wedge moss between the rim of the basket and the liner.
4. Trim foliage stems to 8 inches long; insert them into the sides of the foam so that they extend beyond the basket rim.
5. To create depth, cut one hydrangea stem to 2 inches long and tuck it into the center of the foam. Cut two more hydrangea stems, each 4 inches long; insert them into opposite sides of the foam so they drape over the basket rim.
6. Cut the stems of three sunflowers and three pale yellow roses to 8 inches long. Insert one sunflower next to the handle on the left side of the basket; allow it to extend beyond the rim. Insert the other sunflowers, forming a triangle around the foam. Add pale yellow roses at each end and a third on the right side near the handle, so they drape over the basket edges.
7. To create height, cut the remaining flower stems 10 to 12 inches long, filling in between the shorter blooms. The tallest flowers should extend no higher than 2 to 4 inches above the basket handle. Poke in cornflowers.
8. Insert short blackberry stems to drape over the rim of the basket.