The thing that kills a lot of peoples frontside 180’s and makes it super tough to get 360’s is pushing the rotation with the hips. Loads of people start by opening up their arms towards the rotation too early and then when their back arm starts to point down the slope they initiate the rest of the rotation with their hips. They get all twisted up and find it really tough to get the board around.
With snowboard rotations you want the ability to work your upper and lower body in unison as well as separately. This is because certain tricks require different body movements and positions.
Sure you can spin a separated 180, but you’re going to find it tough to transition to a 360 if you do not sort out the efficiency of the rotation. Check out this video below.
If I open up my arms towards the rotation early my back arm blocks the last part of the spin. I think of the timing as waiting for my board to reach the lip of the jump. I then bring my arms into play. I imagine that my back arm plans to only go as far forward as my back pocket. At that point everything will spin in unison. Sure if I go for a grab etc it will come forward, but I plan for it not to reach too far ahead of the board.
You can try and grab indy to help isolate the back arm, but that may be a lot to think about initially. Just focus on chilling out the arms until you get to the lip of the jump and being patient as you start to initiate the rotation on a jump. You do not need to rush and overpower the spin. It’s only a 180.
Here is an extra article on your back arm and how it effects your riding as well as your freestyle.