Complex sentence: Prior to the large-scale use of drydocks (building or graving docks) for constructing ships, most vessels were constructed on a slipway, i.e. an inclined building platform sloping toward a body of water into which the ship would be launched.
Split into simpler sentences: Prior to the large-scale use of drydocks (building or graving docks) for constructing ships, most vessels were constructed on a slipway-an inclined building platform. It was sloped toward a body of water into which the ship would be launched.