Here is an ambush setup that will work very well. The red dots are where claymores go, the black dot is their spawn point, and the blue dot is your position. The claymores protect the flanks, the alleyways give you a place to duck for cover, and being close to their spawn provides plenty of targets.
In a CQB map, this sort of pattern is often repeated. Look for area like this where you can protect your flanks and take cover.
In a spot like this, you should be able to get 5 or more hits before they get you.
Start to try and predict where the next person will be coming from, and your hits will go up.
Here is the entire map, and just a small sample of the number of places you can set up an effective ambush using two clays. if there are 3-4 people setting up ambushes like this, and going to new spots each time they morph, the opponent will be unable to move quickly, because they will be looking for the next ambush. The red dots are ambush positions, and the blue dots are where the clays go to protect the flanks. You can arrange the clays in different positions each time you use the same spot, just to keep them guessing.