What shape are baked meringues used as pastry layers most often?

Baked meringues used as pastry layers are most often shaped as rounds because this shape provides several advantages in both aesthetics and preparation. Round meringues are traditionally easier to form and have a uniform thickness, which ensures even baking and a consistent texture throughout. This shape also allows for easier stacking and layering when building pastries like pavlovas or in between cake layers, facilitating a pleasing presentation. Additionally, the round shape is visually appealing and aligns with common expectations in dessert design, making it a favored choice among pastry chefs.

In contrast, while square, rectangular, and oval shapes can be used, they don't have the same balance of practicality and visual appeal, which is why they are less commonly seen in the context of baked meringues as pastry layers.