Many people (including myself) have a hard time finding these medals.
I found a way that will almost certainly reward you with one of these medals.
Firstly attack lvl 1-4 valleys,it doesnt matter if it is a lake or flat, whichever valley will do.
Secondly send only warriors and archers nothing else.
The number of the soldiers you must send depends on the level of the valley,but in general these should do:
lvl 1 valley : 50 warriors 20 archers
lvl 2 valley : 70 warriors 30 archers
lvl 3 valley : 90 warriors 40 archers
lvl 4 valley : 120 warriors 80 archers
Finnaly make sure you give valleys time to recover their troops.
Using this combination i got 7 rose and 4 lion medals in an hour.
I hope this will help you.