In this case about all we can do is make an educated guess.  Although lots are often mentioned in the Bible and other ancient literature, the authors seem to take the concept for granted and provide few details.

Ancient "lots" make have taken a variety of forms. The word "pur" (which, by the way, is used in the Bible only in the book of Esther.  The more usual Hebrew word for "lot" is  goral) appears to be derived from an Akkadian word for stone.  It seems likely that the general idea was to take two or more stones of contrasting color or distinctive marking and throw them from a container onto the floor or other surface. The outcome would depend on how the stones happened to land. Details of interpretation probably varied with local custom and the sort of decision to be made. In Esther 3:7 lots were used to determine the date for the destruction of the Jewish people. Possibly in this case a stone was thrown onto a marked surface, the date determined by where it landed, the equivalent of throwing a dart at a calendar to pick a day.