Check the paper towels you plan to use. It is much easier to make a mask with decent sized paper. Ideally you are looking for something about 300 mm (12 in) wide. (There are ways around using smaller paper but it is a fuss.)
As well as the paper towel mask below we have collected a few other masks worth checking out.
So you need paper towel and elastic bands. You can secure the mask ends with either sticky tape, staples or both. I preferred tape after a bit of experimentation.
Take a sheet of paper towel. Make a 3/4 inch (2 cm) fold on the longer side. Press it down firmly. Then make a similar size fold in the opposite direction.
Carry on folding across the whole sheet. Flatten it out and get an elastic band for each end.
Fold over the end with the rubber band on the inside of the fold (bottom picture). The best way I found to fix this permanently was to hold the fold in place with a staple or short piece of tape and then take a longer piece of tape and go right the way round - VERY strong!
Now gently open up the concertinaed mask (top picture) and pull into shape and then...
The final result this time was "OK". Trial and error really helps perfect the mask
You can make the mask a lot more comfortable once you have found the right size or quantity of elastic bands. If you don't have larger bands and the mask is too tight, you can loop a band through another to loosen things up.
I dumped my original, slightly simpler design for this current version from Esco Life Sciences which may also be based NHK's version (see their video - just 17 SECONDS - pretty impressive). There is also a version made with a coffee filter and ... something else (not sure what) but it looks very good. If you have a sewing machine then the third link looks fun.
If you are talking to someone who has Covid-19 then the OUTSIDE of the mask can easily pick up virus contamination. The best way to deal with the mask is to not touch the outside at all and just bin it. So, for me, paper towel is the best bet. Once you have used the mask you can then just throw it away. They cost less than a penny so ... No probs!