CRJ-700 First Officer reported altitude overshoot resulted in GPWS alert and a CFTT event.

Narrative

Person A was pilot flying (PF) and Person B was pilot monitoring (PM).On the arrival into ZZZ we were being vectored for the visual to Runway XX. We were given a left turn from the downwind to a pseudo left base leg and given clearance for the visual approach XX. Upon receiving this clearance I selected 1900 feet in the altitude selector as we were outside of ZZZZZ for the next point on the approach. We were simultaneously slowing and configuring the aircraft at the time and did not notice the aircraft had descended to 1600. We received a caution obstacle" alert off of the GPWS from the Tower in line with the LOC of Runway XX. Visual contact was kept at all times and we continued the left turn to the approach course and landed safely.The primary reason behind this issue was the compression of time due to the late configuration.From my perspective; this issue began on the downwind leg. In retrospect; I would have preferred to start slowing down and configuring much earlier to prevent us from becoming overwhelmed with tasks."