The 18th century Indian painting of Maharana Amar Singh and others watching musicians and acrobats utilizes the two most basic of visual clues for applying depth on a flat surface. They are .

Overlapping.

Explanation:

'Overlapping' is demonstrated as the art form in which one object is placed over another simultaneously. This method is employed in two-dimensional artistic expressions to add depth and intensity to the work.

As per the question, the 'visual clues' that have been applied to inculcate depth onto a flat surface exemplify 'overlapping' as the pictures('musicians and acrobats along with the King Maharana Pratap') are placed over one another to provide illusionary depth into the painting that makes it more appealing and eye-catching which enhances the artistic expression of the work. Thus, 'overlapping' is the answer.

soft,hard and rough for soft would be a pillow or a stuffed animal hard wood floor or a table rough paint