>>3472902diffusion panel is basically just a white surface that diffuses/reflects light
doesn't have to be fancy, can be cheap diy
https://fstoppers.com/business/diy-diffusion-panels-less-30-31069diffusion fabric off amazon
https://www.amazon.com/ALZO-Diffusion-Finished-Scissor-Cut-Photography/dp/B00XPUV1XM/ref=sr_1_5?keywords=diffusion+fabric&qid=1556758899&s=gateway&sr=8-5, or just a white bedsheet, stretch over a picture frame,shoot flash through that
more layers for more diffusion
want even softer light? natural north window light through diffuser (though can be hard to control brightness unlike flash)