I will create a border from the letter y. Choose whichever you like. This dingbat is all corners but we'll throw the corner away and just use the border! Apply the text entry on the 'edge' layer. Select a dark color. Size it to fit the width of space. Don't worry about length.
With the Selection tool, drag a rectangle around the corner and bottom edge of pattern as shown above, and cut it away (anti-alias should be unchecked). Place curved edge on right using Image > Mirror.
Use the Move tool to drag the border into position along the edge of gingham.
Do Edit > Copy and Edit > Paste as New Selection to paste a copy of the border directly below it with pixels aligned like it's one piece. Repeat as needed to fill the length of your page.
Add a drop shadow to the edge for a 3D effect. Use the Magic Wand tool to select INSIDE the design. Use tolerance of 0, no feather, anti-alias checked. If Magic Wand doesn't grab the whole space on first click, hold Shift key down and click again until you have all of inside border. We'll need to expand the selection to include the outline. Do Selections > Modify > Expand. Expand by 2 pixels or more depending on your image.
Do Effects > 3D effects > Drop Shadow. Set Vertical to 0. Use black with other options set appropriate for size of your border.
