Can the shape and orientation of a large glacial rock deposit indicate glacial flow direction

Yes, it can. There are large, elongated mounds of till carried by the glacier as it advanced and left behind as it retreated. These mounds are called drumlins. Their long axis points along the track of the now vanished glacier. They are wider, higher and steeper at the end which points toward the glacier's source and taper away gradually at the opposite end, which points away from the source. They vary in size, but are sometimes a few hundred yards in length and about 50 or 60 feet high. Most are smaller. Sometimes there is a group of them, called a drumlin field. Glaciers also leave behind mounds of debris transverse to their track called terminal moraines. A terminal moraine is formed where the end of the glacier was stationary for a while when it was retreating, and there may be several of them at intervals along the retreating glacier's track.