The stories he wrote about pocket universes are all quite entertaining. One is called "lava lamp world".
The way Farmer (a professor at Indiana State University) did it was to simply have folks create a "pocket universe" ~ looked just like the real universe, and you could see all the distant galaxies and so forth, but it only extended out to the Oort cloud where it simply ended ~ the rest was just an image.
Russell Humphreys (Los Alamos) submitted an interesting model that invoked time dilation/Relativity to explain the Creation event. Crudely put, time is affected by Gravity (This actually has been demonstrated by comparing the measurements from atomic clocks at Sea Level to those at high altitudes). If one takes the Creation event as defined in Genesis 1, and place all of the Created matter (from Day 1) within a half-light year radius the gravity at the center (call the center, 'Earth') is much higher than that on the outer perimeter. At Day 2, some of the matter gets 'pushed' farther out (e.g., 'the heavens were stretched out'). The clocks on the outer perimeter run much faster than the clocks in the center. Day 4, when light from the stars appear on Earth corresponds to 'billions' of years at the outer perimeter...
This my crude summary. You can find more details at answersingenesis.org if you are interested (just search for Russell Humphreys; or Time; or Relativity;...)
Isaiah 40:22 It is he that sitteth upon the circle of the earth, and the inhabitants thereof are as grasshoppers; that stretcheth out the heavens as a curtain, and spreadeth them out as a tent to dwell in: