Raccoon did not like being on his tummy, but Robin doesn't mind. With both, I've found ways to sneak in extra tummy time.
1) Flat on the floor - definitely the least popular and the most work for the baby. Nothing sneaky about this option.
2) Propped up on a pillow - When they're little, put the baby in a kneeling position with arms hanging over the pillow edge.
3) On his/her tummy on my chest - I recline against pillows, decreasing the angle as my baby gets
4) On a large ball - put baby on his/her tummy (I also use a blanket or towel to keep them from slipping) and roll very slowly forward, backward, left, and right. Hold the baby securely at all times.
5) Hold the baby securely with both hands and fly them through the air on his/her belly (I put my arm under from tummy to chest, then put my other arm across the chest). Then "fly" them through the house this way. Once they're less wobbly, it's a great way to chase older siblings. We call it "Super Baby."
6) Gently rolling your baby over (first one way then the other), gives them some brief tummy time in the middle.
7) Make it into play. I figure that the more fun it is for them, the longer it will last.
Disclaimer: Use your own judgment about what's best and safest for your baby.