Alex Raymond made the sunday pages of his Flash Gordon from January 7, 1934, to April 30, 1944: a total of 554 plates. They consist of episodes that follow each other, without well differentiated conclusions. Although each plate had a title, you find them here classified by their content, even if that classification is somewhat vague; this follows a very good edition of the 80s published in Spain by B.O.
You have here an excellent biographical scketch of Alex Raymond written many years ago by José Luis Rodríguez. He complemented it with a formal analysis of the Flash Gordon series, of its plot and its drawing.
The index of all plates by Raymond follows below.
EL FIN DEL MUNDO. 16 planchas, 7-I-34 a 22-IV-34
BARIN, EL PRÍNCIPE REBELDE. 32 planchas, 29-IV-34 a 25-XI-34
EL TORNEO DE LA MUERTE. 14 planchas, 7-I-34 a 22-IV-34
FLASH GORDON, REY. 8 planchas, del 3-III-35 al 21-IV-35
AZURA, LA REINA DE LA MAGIA. 25 planchas, 28-IV-35 a 13-X-35
LUCHA CONTRA MING. 25 planchas, 20-X-35 a 5-IV-36
EL MAR DEL MISTERIO. 27 planchas, 12-IV-36 a 11-X-36
LA SELVA EN LLAMAS. 16 planchas, 18-X-36 a 31-I-37
LOS CAVERNÍCOLAS. 11 planchas, 7-II-37 a 18-IV-37
EL REINO FORESTAL. 16 planchas, 25-IV-37 a 8-VIII-37
LA LEGIÓN DEL DESIERTO. 16 planchas, 15-VIII-37 a 28-XI-37
LOS CONJURADOS. 18 planchas, 5-XII-37 a 3-IV-38
LOS TÚNELES DE LA MUERTE. 30 planchas, 10-IV-38 a 30-X-38
VUELTA A ARBORIA. 18 planchas, 6-XI-38 a 5-III-39
EL REINO DE FRIGIA. 9 planchas, 12-III-39 a 7-V-39
LOS GIGANTES DE LAS NIEVES. 14 planchas, 14-V-39 a 13-VIII-39
EL MONSTRUO MALDITO. 24 planchas, 20-VIII-39 a 21-I-40
RETORNO A FRIGIA. 11 planchas, 28-I-40 a 7-IV-40
LOS TÉCNICOS DE MONGO. 38 planchas, 14-IV-40 a 29-XII-40
EL FIN DE MING. 26 planchas, 5-I-41 a 29-VI-41
RETORNO A LA TIERRA. 16 planchas, 6-VII-41 a 18-I-42
DESIRA, REINA DE TROPICA. 17 planchas, 25-I-42 a 19-IV-42
BRAZOR, EL USURPADOR. 16 planchas, 26-IV-42 a 1-XI-42
FUGA EN EL DESIERTO. 13 planchas, 8-XI-42 a 31-I-43
GUNDAR, EL SALTEADOR. 11 planchas, 7-II-43 a 18-IV-43
LA RECONQUISTA DE UN REINO. 18 planchas, 25-IV-43 al 22-VIII-43
LA TRAICIÓN DE PEQUIT. 18 planchas, 29-VIII-43 a 26-XII-43
EL FIN DE BRAZOR. 33 planchas 2-I-44 a 13-VIII-44 (última plancha dibujada por Raymond, 30-IV-44)