How to put several gif image into one single gif

[Ofnuts]

Ah that's different, I thought you were merging animations...

For this kind of thing;

Manually:

• open the first file
  
• Image>Canvas size and enlarge the canvas to fit the other images (you can specify the size as a formula: 40*4 so you don't have to compute it yourself
  
• File>Open as layers and load the rest, then move each layer to position (possibly using guides to make things easier).
  

With a script:

• Assumes your images are named in the same order as they appear in the final image, by row or column
  
• Install ofn-tiles that you get here.
  
• File>Open tiles... and give the directory where your files are
  
• See HTML file in ZIP for additional hints
  

However:

• Each GIF has its own "colormap" limited to 256 colors.
  
• If the images have more that 256 colors between them some colors will go and this will degrade quality
  
• In the manual process, the first image loaded set the colormap for everything else, so intense color loss can happen in the following images.