Makkos 3:12

A person is lashed as follows: the hands of the convicted offender were tied to the sides of a pillar. The synagogue attendant grasped the offender’s garment to remove it until he exposes his heart; if the clothes are ripped or torn, so be it. A stone was placed behind him, where the attendant stood with a leather strap in his hand. This strap was folded into two and then again into four, with two additional straps rising and falling on it.

Makkos 3:13

The handle of the lash was a handbreadth long and the strap itself was a handbreadth wide; its length was so that the end of it reached his navel. He struck the offender one-third of the prescribed lashes on his front and two-thirds on his back. A person is not lashed while standing or sitting; he is only lashed in an inclined position (i.e., bent over the pillar) as per Deuteronomy 25:2): “so that the judge will make him lie down.” The one who administers the lashes strikes the offender using one hand, as hard as he can.