Yes, you can send letters with attachments in Slowly. You have the option to attach both photos and audio notes to your letters. However, a permission-based system is in place, which means you must first gain permission from your friends before sending them attachments.
For detailed instructions, please refer to the following links:
Slowly will request permission to access these resources upon your initial use of the Camera, Photo Library, and/or Microphone button. It's important to note that this permission request will only appear once. If you miss it or decide to grant permission later, you can navigate to your device's Settings, find Slowly, and give permission before continuing.