After the design and materials are selected, the body of the hourglass is blown on a glass lathe to a size appropriate for the size (time interval) of the hourglass.

The frame is made; depending on its design, it may be a single piece or multiple pieces including a bottom, top, and three or four posts. This manufacture depends on the material. If the frame is made of resin, molds may be constructed, the resin is poured in and allowed to cure, the pieces are sanded or otherwise smoothed and polished, and they are fitted together. Frame pieces may be fitted to interlock; or they may be glued, bonded, or welded, again depending on the materials involved.

One of the most common misconceptions about hourglasses is that there is a formula for the quantity of sand contained in the glass. The sand quantity in a given hourglass design or shape is not based on science or a measurement formula. The types of grains, the curves of the glass, and the shape and size of the opening impose too many variables on the rate of flow of the sand through the glass, so the amount of sand cannot be mathematically calculated. Before the top of the frame is sealed, sand is added and allowed to flow through the glass for its prescribed time interval. At the end of that time period, sand remaining in the top of the glass is poured off and the glass is sealed.