There are still some shadows present below, but I think this will be mitigated once I strap the flash onto the SLR. The iPhone camera is surprisingly good and it does fine in a pinch.
The key is to flood the model(s) with enough diffuse light to eliminate some shadows. Diffusing the light also makes for fewer shiny highlights. You can also change the position of your light sources to add depth to the model.
A common mistake people make is using a very low aperture that limits their depth of focus. If one part of the mini is sharp, but the rest is blurry, that’s what’s happening. Best case is to use a tripod and lower the shutter speed. Also, if you have a zoom, move the camera away from the subject and zoom in. This can effectively blur out the background while keeping the model sharp.