Step 2 Hold down Shift + Alt/Opt and drag the line to copy it. This will be the bottom line of the banner. Select the endpoints and join them (Cmd/Ctrl + J). Close the two ‘open’ sides of the banner by drawing two shapes over it. Make sure nothing sticks out of the banner. Select all (Cmd/Ctrl + A) and go Window > Pathfinder > Divide, then ungroup.
Step 3 The banner is now composed of three parts: top, middle and bottom. Select the pieces that belong to the bottom part and choose Add to Shape in Pathfinder. Click Expand. Repeat for the two other parts.
Select all and click on the Reflect tool then, while holding Alt/Opt, click on the guide in the middle. Choose Vertical > Copy.
Step 4 Draw the right–hand side of your central flower or figure, making sure you start on the guideline. Drag as you place the second anchor point, so that you can make smooth, flowing lines that you can then adjust later.
It’s best to place as few anchor points on a curve as you can – this makes it flow better. Reflect the line vertically on the guideline (as in step 3). Select and join the endpoints.