‘And the women, who had come with him out of Galilee, followed after, and beheld the tomb, and how his body was laid, and they returned, and prepared spices and ointments.'
Instead they used the last moments before the Sabbath in order to observe what happened to His body, watching as His corpse was carried into the tomb. Then in order to prepare spices and ointments with which they would show their love for their dead Master, they returned to where they were staying. The idea of the spices and ointment was that for a while they would counteract the approach of decay while the spirit might still be in the body, and keep the corpse from smelling too pungently. It was all that they could do.
The impression we get from the narrative is that they prepared the spices and ointments prior to the Sabbath, but may not necessarily be so. Representing things chronologically was not the fetish then that it is today. They were more interested in what was done than in when it was done. This is something that comes out constantly in the Old Testament where statements are made, and then the narrative goes back to fill in the detail. Certainly we may see that they made certain preparations before the Sabbath, but equally certainly they would want their offering to be fresh when it was offered, and that suggests that they would expect to leave the main preparations until after the Sabbath (any woman would know that). Indeed Mark makes clear that they had to buy more because they did not have sufficient, which was in fact extremely likely. This was not after all something that they had come from Galilee prepared for. So Luke's statement must be seen as applying to all their preparations, both before and after the Sabbath.