Sanhedrin 52 - Burning, Beheading
The following is the procedure for those who are burned. They would place a hard scarf inside a soft one and wind it around his neck. One witness pulls toward himself, the other one pulls toward himself, until the executed opens his mouth, and then they pore molten lead inside. The lead descends into his stomach and burns his intestines.
This procedure is for those who are beheaded: they would decapitate him with the sword, cutting off his head from the front. Said Rabbi Yehudah, "It is a disgrace for him, since the Roman government does the same. Rather, they chop it off with an ax." Answered the Sages, "That would be even more disgraceful."
But how do we know to cut off the head, and not, say, stab him? - Because it says, "... by the edge of the sword ..." Then let's cut him in half!? - Said Rab Nachman, "... And you shall love your fellow as yourself ..." means to choose a favorable death for him.
Art: Edouard Manet- Boy with a Sword