Edit the IJK to RAS Matrix in 3D Slicer

I am working on registering two nrrd files. I have noticed that one of the images appears flipped in the x and y direction resulting in inaccurate registration results. The two volumes have different IJK to RAS Matrix. One of the images has a diagonal of 1,1,1, and the other has a diagonal of -1,-1,1. I was initially applying a linear transformation but that appears to transform all 3 views of the image rather then just the x and y.