Alvar Aalto's Vuoksenniska Church (1958) has been widely discussed in architectural literature, often in general terms of plasticity or ambiguity. Yet previous studies have given relatively little consideration to the approximately 800 archived sketches and drawings for the project. When a limited number of Aalto's sketches for the church have appeared previously, an isolated sketch has often been used to illustrate a single aspect or element of the church, such as a notable lighting or acoustic detail. The church's complexity and spatial qualities make it well suited for more detailed study, using sketches and drawings to clarify the design process of the church and provide new insights. The most important sketches and drawings from the church's design process are presented and discussed in this paper. They illustrate how the design process began with simple sketches, in plan and section, for folding and moveable partitions, highlighting Aalto's priority for balancing religious and social activities in the church through divisible meeting spaces. Acoustical considerations were also combined in these earlier plans, while section sketches show how the church's skylight and unique clerestory windows were gradually developed through several iterations. The threefold repetition of elements in both plan and section was consistent throughout the design process. The structure of the church was designed with simple organic motifs like frogs and fish, but was also intentionally combined with other key elements. While previous studies have emphasised one aspect of the church or another, Aalto's sketches taken together offer a more holistic understanding. They show the interrelated nature of different elements in the church and the relative relationships between different sketches and ideas in the design process. As a work of architecture, the church's definitive qualities of architectural harmony and coherence are far more compelling than any one particular feature or notable detail.