See this link for an introduction on time stacking and time slicing.
time_slice.R requires the number of pixels wide or tall the image is to be a multiple of the number of images in your timelapse.
time_slice_v2.R attempts to get around this. Some images will contribute more pixels per slice than others. This is done by making the first x% of the images cover the first x% of the pixels (with appropriate rounding). It does not deal with number of images being greater than the height or width of the images in pixels. Version 2 will probably work better for you.
For example, if the images are 150 pixels wide and your timelapse has 100 images, time_slice.R will make the first image have a slice which is 51 pixels wide. The remaining 99 images will get slices which are 1 pixel wide. time_slice_v2.R will alternate between 1 pixel per i