Slice assembley sentinel-1

dear all, does anyone knows if I can perform slice assembly after performing terrain correction or it should be done on original images before applying terrain correction? Another question is if I want to do slice assembly in batch processing is it possible to add multiple images and run it?

if the images are already geogoded (by terrain correction) you can use the mosaic tool to merge adjacent images. The slice assemby tool is to stitch raw S1 images and will throw an error if you input terrain corrected / geocoded images:

About the batch processing: The operator is designed in a way so that you can add multiple images as long at once, as they are from the same track. If you want to merge images of different tracks, terrain correction and mosaicing is probably the better choice.