Project Gantt charts are a pain to create in PowerPoint. Screen dumps from professional project management software are too detailed and don't have the right look & feel. Manually resizing blocks is tedious, and oh boy, what if you have to add or change an activity...
I often use a disguised stacked bar chart to create project flow charts in PowerPoint.
First, you need to look at the content. Like my approach with all data charts, project plans should not be copy pasted directly into PowerPoint. Project planning, data analysis, is not the same as presenting the result to an audience, you need to disconnect the two activities. This means in most cases starting with a blank sheet of paper.
Purely from the stand point of communication (not planning): which activities should be grouped together, which separated? What is a logical phasing? Sometimes, nitty gritty activity details are crucial for planning purposes (exact roll outs for each city), but can get pretty boring in a presentation. Sometimes the opposite is true, a small pilot might be worth highlighting in the presentation.
Once you have this sketch, you can transfer it to PowerPoint. PowerPoint does not have pre-configured Gantt chart templates, but the stacked bar chart can provide a solution. See the chart below as an example:
It takes a bit of thinking to set up, but once in place, it is easy to make small changes to the length of the bars and/or add and subtract activities without having to go through the hassle of lining up everything again.
Feel free to copy the design, or download the above slide from the SlideMagic template store.