Padlet is a great virtual pin-up board that you can use for your design and collaborative work. The Timeline format in particular is great for making an Experience Flow as you can present the different points in the experience of your design solution in a horizontal timeline.

Check out our example here.

A slideshow on Google Slides or Powerpoint is an easy way to present an idea sequentially.  You can use it to describe a sequence of events in a service or  experience, or the  different parts of a material or media that users will go through. In this example, Slides were used to roughly describe the different sequences in a series of learning videos.

You can use Canva to "sketch" your idea by creating mockups of what products, websites, infographics, posters might look like. In this example, Canva was used to prototype the look and feel of an event poster before and after an initial round of feedback. 

Photo by dix sept on Unsplash 

You can also just grab your pen and paper and sketch! It doesn't have to be well drawn -  as long as it can convey the general idea of each part of the Experience Flow.  This way you can clearly convey your idea in as little as 10 minutes or less.