Channel and slab waveguides were fabricated by thermal Ag+/Na+ exchange in glass and buried by field-assisted diffusion. The mask was fabricated in a two-step photolithographic process by means of low-cost optics. A procedure to thinly and accurately slice samples with standard cutting and polishing machines is demonstrated. The two-dimensional index distribution of the sample slice was measured by a commercial polarizing interference microscope using a light-emitting diode as light source. The index profiles are analysed by taking into account the electromigration dynamics. The main finding is that the index peak of a channel waveguide close to a slab waveguide (slab-sided channel waveguide) was found to be deeper than that of a similar isolated channel waveguide. A preliminary application is proposed to improve the coupling efficiency between the channel and slab buried waveguides used in some integrated optical devices made in glass, such as arrayed waveguide gratings.