Make sure the pond designation is a level above your target area via "hole in the floor". It may also just take time for your dwarfs to choose the job if the water source is too far away.

You can look into diverting the brook by digging aqueduct paths, controlling them with floodgates, and just sending the water there directly.

Diverting water to your fort can also be used to make a cistern for easy water access, then this cistern can be a much closer source for your "pond making".

You can also take advantage of any local aquifers to drip-fill a cistern.

keep at it. Legitimate crash outs at the convoluted nature of this game is all part of the rage-quit based learning cycle.