1. Open the Shortcuts app on your iPhone (it's already preinstalled).
2. Tap the plus icon in the top right corner.
3. Select Add Action.
4. In the search bar, type Open app and select the Open App app.
5. Tap Choose and select the app you want to customize. For example, Facebook, Spotify or the Messages app.
6. Tap the three dots in the upper right corner. From here, give the shortcut a name and tap Add to Home Screen.
7. Where it says Home Screen Name and Icon, rename the shortcut to anything you'd like.
8. Next, go to the Safari app to find a new icon image. You can search for something like the Facebook icon aesthetic. When you find an image you like, save it to your photos.
9. Go back to the Shortcuts app and tap the current icon. Select Choose Photo and tap on the image you just saved. You can zoom in or out on the image. Tap Choose.
10. Tap Add.
Now you have customized apps on your phone. The original apps will remain on the phone, but you can store them in a folder.