A sample, or slide, retaining tray includes a reagent reservoir, or recess, and a reaction chamber. A slide, or other sample container, can be positioned on the sample retaining tray as desired, with a tissue specimen face down, between a platen on the tray and the slide. A reagent from the reservoir is rendered flowable, such as by heating, and flows from the reservoir into the reaction chamber. Optionally, reagents or other fluids can be provided from above, by dripping onto a drip surface of the sample retaining tray, or below via an inlet port in the platen.