Sure thing. First, line up the stones with the true arch shape before you start carving— that gives the weight you need. Then use a hidden false eye in the keystone— a small notch that lets you slide the outer part of the arch in later so you can keep a clear line of sight. Make the outer face a bit thinner than the inner, so the arch looks solid from the front but lets you peek out from the back. Keep the mortar thin in the visible parts, but add a bit more there to hide the joint on the side. And always finish the inside with a tight joint— that’s what holds the whole thing together while the outside looks open.