I dont know what is best way but I have used white wood glue (PVAc) for that kind of works. This glue is IMO best for gluing leather because its flexible and penetrates well. One good way to avoid glue coming through the leather (glue would make ugly spots) is first impegrate leather sheet thoroughly with thinned water based tapestry paste and then let it dry properly before applying the glue for installation.

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