You could use something such as a shot glass (make sure it’s been boiled first to remove anything harmful) and bury it in the gravel/sand to make a little cave, your corys should be able to access it and use it to get away from the other fish.
If you want to go "natural" use chunks of bogwood like Malaysian Driftwood; some of the pieces (being real wood each is different) have crevices and tunnels and catfish enjoy these. Thick plants help too.
This is natural behaviour, though usually only seen at feeding time. Both the ram and the cories feed from the substrate, and it is normal for a ram to "push" the cories away from "his" food. This is not serious provided it does not develop beyond this. If you had a pair of rams and they spawned, the same behaviour would be seen obviously to protect the eggs/fry. If the ram however is attacking the cories regularly, that may require more direct intervention as the annoyance can cause cories to become stressed which leads to physiological problems.