The present invention relates to an ostomy appliance comprising a front wall and a rear wall of flexible material forming a bag, said rear wall having an opening for receiving a stoma, and being provided with an adhesive wafer for securing the appliance to a users skin, said wafer having a hole being aligned with the opening for receiving the stoma, wherein the opening of the rear wall has an edge being adapted to be secured to a surface of the adhesive wafer facing away from the user in an attachment zone surrounding the hole of the wafer, and wherein a first part of the edge of the opening of the rear wall is permanently secured to the surface of the wafer in a corresponding first part of the attachment zone, and a second, remaining part of the edge of the opening of the bag is prepared for adhesive sealing of the same to the remaining second part of the attachment zone. This allows for a simple evaluation of the stoma area for cutting the wafer for adapting the same to the specific stoma and manipulation and location of an adhesive wafer in relation to the stoma is enabled.
