An apparatus for electroplating a semiconductor wafer includes an insert member configured to circumscribe a processing region. The insert member has a top surface. A portion of the top surface of the insert member has an upward slope that slopes upward from a peripheral area of the top surface of the insert member toward the processing region. The apparatus also includes a seal member having an annular-disk shape. The seal member is positioned on the top surface of the insert member. The seal member is flexible such that an outer radial portion of the seal member conforms to the upward slope of the top surface of the insert member and such that an inner radial portion of the seal member projects inward toward the processing region.