How to design the table tennis round robin flow chart 19 into 8

First, three players from 19 were selected to form a family to decide 1 player for round robin, and then the remaining 16 players were divided into eight groups, and two players in each group were directly eliminated by PK, so eight players were decided in eight groups. Then draw lots for these nine players, and select two players for another PK elimination, so that only eight players can advance to the next round.