Mix the stevia and xanthan gum together in a small mixing bowl and set aside.
Pour the agave, lemon juice and water into a high-powered blender (like a Vita-Prep). Cover and blend until well combined. Add the stevia and xanthan mixture to the blender. Cover and blend on low until the mixture is well combined, about 10 seconds. Turn off the blender.
Add the still-frozen strawberries to the blender. Cover and blend on high while pushing the strawberries down into the blade with the wand until the mixture is smooth but still frozen, about 5 to 10 seconds.
Spoon the strawberry ice into paper cups or chilled bowls and serve immediately.