How would you describe the slice that created the rectangular cross-section on this cake?

In order to obtain the rectangular cross-section on this cake we need to do slicing:

Parallel to the base.

We know that when slicing is done parallel to the base than we get a cross-section that is similar to the base ( i.e. of same shape and size).

Hence, here we have a cake in shape of a rectangular prism or we may say a cuboid so in order to get the rectangular cross-section we need to cut this cake parallel to the base.

Hence, the answer is:

Parallel to the base.

check the picture below.

three-fourths of an hour

36÷48=0.75

0.75=