One of the most underrated features on iOS and Android has always been keyboard shortcuts, or text replacements. This allows users to easily expand something such as FreeBusy availability link on mobile by typing out shortcuts like “@@”, or “##” for example.
iPhone & iPad: How to customize keyboard shortcuts
Copy your FreeBusy availability link - your FreeBusy page or your event template link
Open up Settings > General > Keyboard > Text Replacement.
Tap the + button up top to add a new text replacement
When adding a new text replacement, paste the FreeBusy availability link in the Phrase box, then add the desired text shortcut in Shortcut box (for example “@@“). Make sure it’s something you won’t type on a daily basis or something you will forget.
Tap the Save button when done.
Android: How to customize keyboard shortcuts
Copy your FreeBusy availability link - your FreeBusy page or your event template link
Open up Settings > Languages & Input > Personal Dictionary
Tap the + button to add a new text replacement
Tap the line at the top and Paste your FreeBusy availability link
Tap the line next to labeled "Optional shortcut" and then type the shortcut you want to use for your availability link. For example, you could use “@@“.
Tap the Save button when done.
Now whenever you want to easily share your FreeBusy availability link, just type “@@“ and you’re done.
NB: If you're using a keyboard other than the default keyboard, it may not support text shortcuts, or the settings may be different.