The 3 letters s, w, and x of the dingbat EZ Border can be combined to build a mat that looks like a torn edge (shown above). Size and color this corner border to fit your page. I'm using deep sage.
First, create a border corner by applying each of the 3 letters separately and assembling them into a corner shape. Next, copy the corner shape, paste a copy as a new selection, mirror the copy, and place it next to the first corner before de-selecting. Now we have a half-border.
Copy this half border, and paste it as a new selection. Flip the copy and position it next to the other half for a complete rectangle shape.
Select the interior of 'mat 1' with Magic Wand — tolerance 0, feather 0. Do not de-select yet. Create a layer above 'mat 1' and name it 'mat 2.' Enlarge your selection by 3-5 pixels depending on how much of mat 1 you want to show. Do Selections > Modify > Expand. Fill selection with white. De-select.
Add a rectangle accent border to the white mat with Preset Shape tool and a 1 pixel solid line. Select the same color as mat 1 for your stroke color and no color for fill.
Add a small drop shadow to both 'mat 1' and 'mat 2' layers.
Before we move on, let's merge 'mat 1' and 'mat 2' into one layer so we can keep them together as we move and re-position. Turn off visiblity for ALL OTHER layers and merge visible (Layers > Merge > Merge Visible).
Right click and rename merged layer 'journaling mat.' Turn visibility for all layers back on.
