Red Goblin #3 features a two-page flashback (with Norman & Normie Osborn) that is explicitly stated to be "two years ago." The 4:1 ratio would imply this scene takes place around comics published in June 2015, which... suprisingly fits despite ASM6's chaotic internal timeline.
The scene appears to be before Go Down Swinging, given Norman is still evil and Normie doesn't mention being transformed into Goblin Childe, still obeying his grandpa. From ASM4 3 to ASM4 28, Osborn is forming the Goblin Army and rid of the Goblin Serum, desperately trying to become the Goblin again from ASM4 32 to ASM 796. He's Carnage from ASM 797 to ABSCRNG 5, and is rid of his sins in ASM5 50 shortly after RAVENCROFT.
Between Secret Wars and ANAD seems like a good spot; also, Norman appears in a one-panel cameo in SECWARS 1 (also as "oz @amazinghair.net")
GREEN GOBLIN/NORMAN OSBORN JR.
...
W&X2 12
ASM3 17.1
ASM3 20.1
[SECWARS 1] <– ADD
RGOBLIN 3-FB <– ADD
ASM4 3
...
OSBORN, NORMIE
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SUSM 31
RGOBLIN 3-FB <– ADD
ASM4 7
...
Red Goblin #3 flashback
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Red Goblin #3 flashback
~ Dot