The 3D modeling technique presented in this paper, predicts, with high accuracy, electromagnetic fields and corresponding dynamic effects in conducting regions for rotating machines with slotless windings, e.g. self-supporting windings. The presented modeling approach can be applied to a wide variety of slotless winding configurations, including skewing and/or different winding shapes. It is capable to account for induced eddy-currents in the conductive rotor parts, e.g. permanent magnet eddy-current losses, albeit not iron and winding AC losses. The specific focus of this paper is to provide the reader with the complete implementation and assumptions details of such a 3D semi-analytical approach, which allows model validations with relatively short calculation times. This model can be used to improve future design optimizations for machines with 3D slotless windings. It has been applied, in this paper, to calculate fixed parameter Faulhaber, Rhombic, and Diamond slotless PM machines to illustrate accuracy and applicability.