Question: How do I plot objects opaquely "in layer order"?

I'm am pretty new to maple, coming from a mathcad background, so sorry in advance if this is a dumb question.  My original need was to plot text objects with sold backgrounds on top of other plotted objects.  I saw in other posts that Maple doesn't natively support this.  So instead I'm trying to create a composite plot of objects by plotting text objects over polygons or rectangles.  However I can't seem to make a given plotted object "cover" another plotted object.  

Below is a simple example.  The easy analogy is just that I want to plot these objects in “layer order”, with L1 being the top layer.  So I would like the polygon to opaquely obscure the “underlying” contour plot, and then in turn, the text object to behave as a “top-most layer” with the polygon acting as a background for the text. 

L1 := textplot([2, 2, "Polygon"], color = white);

L2 := polygon([[0, 0], [3, 4], [3, 1]], color = red);

L3 := contourplot(x^2 + y^2, x = 1 .. 2, y = 1 .. 2);

display(L3, L2, L1);