I'm not sure if the orientation is correct but I believe the bottom left symbol might be 制. This is as clear of a shot that I can get of the stamp. Please and thank you.
About 500 years ago, ceramics in 荊溪 County became famous. If your teapot is genuine, it should be worth a lot, at least several hundred dollars. 荊溪 is a county under the jurisdiction of Changzhou City, Jiangsu Province, where the ceramic products are very famous. Between 1970 and 1990, Jingxi County produced many ceramics. The maker stamped a mark on the bottom of the ceramic. This pot was made by a businessman surnamed 张.