Is it on a solid suface? I have a number of large containers and I just drag them around as needed. And most of mine are on grass or mulch.....the ones on concrete, gravel or pavers are much easier to move around :-)

@gardengal48 The 300 lb pot sits on a slate patio, it cannot be dragged because it would damage the surface of the slate.

Then you need a hand truck. And one that is bowed or dished to accommodate trees and large containers, aka a landscape hand truck.

There are heavy duty plant dollies available you could purchase that would lift the pot off the slate and then make it easier to move about. However IME, the casters never hold up to the weight for very long and inevitably fail.....and then you are back to where you started ;-)

I would look at industrial capacity dollies, and if you don’t find one that suits aesthetically, get heavy weight rated castors and have one constructed. DH had a 3000 lb industrial lathe sitting on a pair of homemade dollies for close to 5 years while he refurbished it and they held up just fine. Just have it constructed to shelter the casters from the worst of the weather, and then do regular lubrication of the casters.

https://www.amazon.com/Dollies-Heavy-Duty-Material-Handling-Products/s?ie=UTF8&page=1&rh=n%3A256347011%2Cp_n_feature_keywords_browse-bin%3A3363748011

...or plant something different in the pot that will look striking and artistic growing non-uniformly.