The Ultimate Berry Crumble
You can use self-rising flour and skip the all-purpose flour, salt, and baking powder combination.
Use any variety of berries; ripe peaches and other summer stone fruit would also be fantastic. You can use frozen berries, which are a lot juicier, so keep that in mind when making cornstarch-related decisions.
If you want a pie-like filling, you'll want to toss in about 1 to 4 teaspoons of cornstarch, otherwise for a runnier fruit mixture cut it in half, or leave it out altogether.