5 Easy Ways to Create a Border in Photoshop
There are several quick ways to add borders in Photoshop, from simple solid frames to fully customized designs. This tutorial covers enlarging the canvas for a solid color border and using Layer Styles for color, gradient, pattern, and brush-enhanced borders. Use the method that best fits your project and desired look.

Step-by-step instructions
Create a solid border by enlarging the canvas
Open your image.
Go to Image → Canvas Size.
Choose units (pixels or inches). Increase Width and Height by your desired border amount (e.g., +300 px).
Set Anchor to the center so the border is even on all sides.
Set Canvas extension color to Foreground, Background, White, Black, or Other (sample from your image if desired), then click OK.
Add a customizable border with Layer Styles (Stroke)
Unlock the image layer if needed, then double-click the layer to open Layer Style and select Stroke.
Set Position to Inside and adjust Size for border width.
Choose Fill Type: Color (solid), Gradient, or Pattern.
If Gradient, choose a preset and adjust Style and Angle; if Pattern, choose a pattern and adjust Scale and Angle.
Click OK when satisfied.
Select the border area only (for brush effects)
Ensure your Stroke border is applied and sized to leave room for effects.
Select the Rectangular Marquee Tool (M) and set Feather to 0.
Drag a selection from one image corner to the opposite corner to select the photo area (not the border).
Invert the selection: Ctrl+Shift+I (Cmd+Shift+I on Mac) to select only the border.
Paint custom effects onto the border
Create a new layer above your image.
Select the Brush Tool (B), choose a brush (e.g., watercolor) and a color.
Paint within the active selection to stylize the border.
Deselect with Ctrl+D (Cmd+D on Mac).