How to pass SwiftUI container size to the body of subviews?

The child views of my container need to get (not set) the size of container from within their view body, in order to perform some calculation. I've made a custom container that conforms to the Layout protocol (the actual implementation isn't important). The required placeSubviews method has a bounds parameter which is the size of container. Does anyone know whether it is possible to store the bounds somewhere so that the subviews of the container can access it, such as in environment key of the view hierarchy? Or is my only option to use a GeometryReader?

struct CustomContainer: Layout {
    func sizeThatFits(proposal: ProposedViewSize, subviews: Subviews, cache: inout Void) -> CGSize {
        // Calculate and return the size of the layout container.
    }

    func placeSubviews(in bounds: CGRect, proposal: ProposedViewSize, subviews: Subviews, cache: inout Void) { 
        // Tell each subview where to appear.

        // Can I store bounds parameter somewhere??
    }
}