In the Book of Acts, planting churches in unreached areas was the natural application of the Great Commission.
In fact, the logical implication of the Great Commission is that it would be done in the context of the local church wherever it exists and that it would lead to establishing local churches where they don’t exist. Baptism isn’t something that is done isolated from Body life. It is the initiatory rite of a new disciple into the church. Naturally, if a church doesn’t exist and we are pursuing the disciple-making mission, a church needs to be established or we aren’t being faithful to Jesus’ commands. The New Testament knows nothing of a lone ranger evangelist who saves souls and moves on. The church is where disciples are baptized and taught.
This was the approach the apostles took when they were empowered by the Spirit. They established a church in Jerusalem. Then, when the persecution arose against them and many were forced out of Jerusalem, they began making disciples and establishing churches everywhere they went in Judea and in Samaria. Soon, churches were established as far out as Antioch which was a Gentile city. They were fulfilling Jesus’ mandate to be witnesses and to make disciples.