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To foundation-piece, you stitch fabric pieces to a foundation paper with the marked side of the paper facing up and the fabric pieces layered underneath. The resulting pieced units will be mirror images of foundation papers. The diagrams and photos that follow show the right and wrong sides of an arc as it is being constructed.
1. To make a foundation paper, trace the desired pattern onto tracing paper or the foundation material of your choice, including all lines, numbers, and dots. Repeat to make the desired number of foundation papers.
2. Cut out the traced foundation papers roughly 1⁄4" outside the dashed outer lines.
3. Roughly cut out fabric pieces that are at least 1⁄2" larger on all sides than the area on the foundation they will cover. Note: For this example, red 3×7" and tan 5×7" rectangles were cut to cover the triangles on the foundation paper.
4. Aligning long edges, layer a tan 5×7" rectangle atop a red 3×7" rectangle.
5. Place a foundation paper atop the layered rectangles, positioning it so that the rectangles’ aligned edges are 1⁄4" beyond the stitching line between positions 1 and 2 and at least 1⁄4" beyond the foundation’s top and bottom stitching lines (Diagram 1). To check placement, pin on the line between positions 1 and 2, then flip the red rectangle open. Make sure it completely covers position 2 and extends into position 3 at least 1⁄4". If it doesn’t, reposition and recheck until it does.
6. Working with the marked side of the arc foundation paper up, sew on the stitching line through all layers, extending the stitching past the beginning and end of the line by a few stitches (Diagram 1 and Photo A).
7. Press the rectangles open, pressing the seam toward the red rectangle (Diagram 2 and Photo B). Trim the red rectangle only (not the foundation paper) to about 1⁄4" beyond the stitching line between positions 2 and 3 pieces (Diagram 3 and Photo C).
8. Align a tan 5×7" rectangle with the trimmed red piece so their right-hand edges are about 1⁄4" beyond the stitching line between positions 2 and 3 (Diagram 4). Sew on the stitching line (Photo D). Trim the seam allowance if needed; open pieces and press seam toward tan rectangle (Diagram 5 and Photo E). Trim the just-added rectangle (not the paper foundation) to about 1⁄4" beyond the next stitching line.
9. Continue adding red rectangles and tan rectangles in an alternating pattern, trimming in the same manner, until you have pieced an entire arc (Diagram 6 and Photo F).
10. Trim all fabric layers and foundation paper on dashed lines to complete a foundation-pieced unit (Diagram 7 and Photo G).