Start by hammering two nickels. Only hammer enough so the detail disappears. It’s important you use a smooth faced hammer on a smooth surface. Otherwise you’ll spend more time sanding out tiny dings and dents.
Use a pencil to draw out the shape you want. This doesn’t have to be the final design but it helps to guide you along the way. Also it helps if you have an engraver to trace over your pencil mark. That way you marks won’t wipe away while your handling it. If you don’t have an engraver use a permanent marker.