I’ve already implemented Scenes in OH using Rules
Has anyone created an efficient method to trigger those Rules using Alexa?
I was thinking of creating some switch items that would trigger the rules, and expose those items to Alexa.
Your thinking is the general approach.
In the UI you can make a widget whose action is to call a scene directly without an Item, but the only way to expose it to Alexa is through an Item.
The standard way to do it is to create a Settings → Rule that triggers on commands to that new Item with a “Call Rule” action to invoke the scene.
The sneaky way is to edit the Scene itself on the code tab to manually add a trigger to the Scene to trigger on commands to the new Item. A Scene is a rule like any other so it supports triggers,but the UI doesn’t present a way to add a trigger.