In case someone needs this, following @DerkJ 's advice this is what I got working:
Var json_scales As New JSONItem
Var json_yAxes As New JSONItem
Var json_ticks As New JSONItem
json_ticks.value("ticks") = "ticks"
Var json_begin_at_zero As New JSONItem
json_begin_at_zero.Value("beginAtZero") = True
json_ticks.Value("ticks") = json_begin_at_zero
json_yAxes.add(json_ticks)
json_scales.value("yAxes") = json_yAxes
options.value("scales") = json_scales