How to solve a Rubik's cube 4х4 - Step 3
Now the cube become equivalent to the cube 3x3 and we can apply a formula for 3x3 cube In the beginning of this stage you should have the solved centers of the cube and combined pairwise similar pieces of side faces. But at the same time their location is not important.
In the end of this stage you should have the solved upper cross.
Apply the formulae of the first step for the cube 3x3. Do the upper cross. Find couple of pieces of the upper cross and locate the, on the lower face. Now, depending on how the colors were placed, carry out the procedure shown below.
Repeat the operation with the remained pairs of pieces of the upper cross.