It is usually three - dimensional, taking the form of sculpture or installation, though there are a number of minimalist painters as well such as Agnes Martin and Frank Stella (tate.org.uk)
Charles Hinman is an Abstract Minimalist painter who pioneered the concept of the three - dimensional shaped canvas in the mid-1960s. (artsy.net)
As minimalist painter Frank Stella once said: «What you see is what you see» (source). (understandingminimalism.com)