This post contains a whirlwind guide as to how you can add a white border around your photographs in Photoshop and size them appropriately for your Instagram posts.
This is mostly a guide for myself so I don't forget, but hopefully, it helps others who stumble across it!
- Create a New Photoshop Document - set it to 1080 x 1080 pixels. - This is the ideal size for Instagram posts.
Note - You can change the size to 1350 x 1080 pixels if you want a longer image. The caveat here is that it doesn't look quite as good in your Instagram feed.
- Select File -> Place Embedded -> And choose the photo that you want to give a border to.
Position and scale your image so that it covers the entire canvas.
- Once the image is imported, scaled it up to fill the canvas. Then select Layer -> Flatten Image
This will merge the background layer and your image into one layer.
- With the layer now flattened, right-click on Layer 01 -> Convert to Smart Object
- You will then be able to Right Click the layer-> Blending Options -> Stroke -> 20px White. This should add a 20px border around your image.
Play around with the stroke size to see what works for you.
- Finally, select File -> Export -> Save for Web (Legacy).
- Select JPEG format + Maximum Quality (100%).
You now have an image that has a lovely white border around it for Instagram, or wherever else you want to post it for that matter.
You can see a live example of this here on my very own Instagram: