We have investigated methods of assembling large magnetic blocks from NdFeB magnets with a high value of the maximum energy product, and inserting these blocks into magnetic circuits. We found that the magnetic induction in the middle of an air gap between large opposing magnetic blocks in a closed magnetic circuit depends, in addition to other parameters, on the basic method of assembling these magnetic blocks. We compared two methods of assembly, differing in the direction in which magnetic plates approach each other. When being moved toward each other during the assembly by Method 1, magnets first repel each other. In the case of low coercivity of the magnet material, this results in their partial demagnetization. However, by using the new Method 2, where the magnets keep attracting throughout their movement together, it is possible to eliminate partial demagnetization.