Jamieson, Fausset and Brown on Genesis 31:44

44. Come thou, let us make a covenant--The way in which this covenant was ratified was by a heap of stones being laid in a circular pile, to serve as seats, and in the center of this circle a large one was set up perpendicularly for an altar. It is probable that a sacrifice was first offered, and then that the feast of reconciliation was partaken of by both parties seated on the stones around it. To this day heaps of stones, which have been used as memorials, are found abundantly in the region where this transaction took place.