What is the traditional way of having a jalsah for boys who complete Hifz?

Answer

Traditional way is only the Sunnah. In the Sunnah there is no ceremony, no jalsah, etc. for a student who completes Hifz or even the Aalim course. There were innumerable powerful Huffaaz among the Sahaabah. Never did they have any specific way/ceremony/ jalsah to honour the student. Just make dua for the student.

All jalsahs are motivated by riya and takabbur – merrymaking in the name of the Deen.