If I think through the different steps (I will exaggerate to exemplify the difference):
Objectives:
Non-mastery: Multiple objectives within a single lesson e.g. Multiplication and division by 10,100 and 1000
Mastery: Very clear single objective: Division of whole numbers by 10 to give a decimal to 1 dp
Teaching:
Non-mastery: procedural, focusing on 'how to get the answer' to specific question types
Mastery: for understanding, focusing on explaining why the answer is what it is, using a variety of question types to probe understanding. Often, more use of concrete or pictorial representations (though this depends on previous school policy).
Tasks:
Non-mastery: differentiated question sets of different groups within the class (or in different sets, in larger schools). Problem solving only as an extension for the most able. Focus on 'answering questions', not on explaining. Challenge limited by group.
Mastery: limited question numbers, all pupils access different question types as there is variation within these questions, very little differentiation in core task. Focus on explanation in lots of different forms (concrete, pictorial and abstract). Extension is via deeper thinking, not via different calculations with bigger numbers.
May also see in mastery: a separate 'fluency' session where routine skills are practised without necessarily additional teaching, though this is also an opportunity for immediate 'catch up' for any children needing more support after the main lesson of the day, or for 'p[re-teaching' any key skills some children will need in e.g. next topic.