This piece of math recreates the BoxInsetLayout class behaviour for View based UI building on Wear OS in Jetpack Compose. Using this @Composabe will create a Box within the confines of a round display without cutting off the corners.

RoundBoxInset.kt

@Composable
fun RoundBoxInset(content: @Composable () -> Unit = {}) {
    BoxWithConstraints {
        val horizontalPadding = (maxWidth.value - (maxWidth.value / 2.0 * sqrt(2.0))) / 2.0
        val verticalPadding = (maxHeight.value - (maxHeight.value / 2.0 * sqrt(2.0))) / 2.0

        Box(
            modifier = Modifier
                .fillMaxSize()
                .padding(horizontal = horizontalPadding.dp, vertical = verticalPadding.dp)
        ) {
            content()
        }
    }
}