Cómo peinar la hoja de fondo

<style name="BottomSheet" parent="Widget.Design.BottomSheet.Modal">
        <item name="android:background">@android:color/transparent</item>
    </style>

    <style name="BottomSheetMenu" parent="Theme.Design.BottomSheetDialog">
        <item name="bottomSheetStyle">@style/BottomSheet</item>
    </style>
</ProgAli>