Here's a closer look at these church candelabra decorations. Even though you think the cut stems are visible, once you view from a distance you'll no longer even notice.
Keep the stems going straight out from the back. As you move forward, filling in the greenery, you can begin to angle the greenery inward, following the curve of the heart.
Do place the stems securely into the foam - about 1 inch or so. It's not necessary for more than that, or the stems will start crowding each other and could break down the integrity of the foam if packed too tightly.