We present paper II comprising a 35 arcmin^2 JWST/NIRCam imaging and wide-field slitless spectroscopy mosaic centered on J0305-3150, a luminous quasar at z=6.61. The F356W grism data reveals 124 [OIII]+H\beta emitters at 5.3<z<7, 53 of which constitute a protocluster spanning (10 cMpc)^2 across 6.5<z<6.8. We find no evidence of any... Show more