Sure! It is actually free with fastmail, and is the equivalent to "myusername+alias@gnail.com".
I have a custom domain, so i set my email to firstname@mydomain.com. They allow you to use alias@firstname.mydomain.com to alias to firstname@mydomain.com and you can use as many aliases as you want. That is at no additonal charge. To me, that alone is worth it to use fastmail.
I do basically the same thing. Their iOS app works exceptionally well for this flow, remembering that the last place I left it was the alias creation form. I can typically do this in 30 seconds.
Like the parent, I have name@example.com as the official account email for a single user account. All aliases are alias@example.com.
I like Fastmail but they require mobile phone number as your identity is big no to me. Basically you can't have two fastmail accounts on one phone number.
You can't typically cannot have two trial accounts on one phone number. But you can have as many paid accounts as you like with or without a phone number.
I have a custom domain, so i set my email to firstname@mydomain.com. They allow you to use alias@firstname.mydomain.com to alias to firstname@mydomain.com and you can use as many aliases as you want. That is at no additonal charge. To me, that alone is worth it to use fastmail.