When you want to hold a speaker's video feed for all participants, use Spotlight.

You can use Pin a particular video to stay on your desktop, and it will not affect other participants.

Here is a short tutorial on how to use Splitcam to add Timer Color Flags to your online Toastmasters meetings.

1–download, install & run Splitcam (Update (5/21/19): The video & steps refer to older version. To download the older Version 8.1.4.1, click here.)
2–in your online meeting app (ie Zoom/RingCentral) choose Splitcam as your camera (instead of the webcam)
3–in the Splitcam dashboard, click on Source > Webcam, then choose your desired webcam & resolution
4–to use the Picture-in-Picture function, click on the PIP Mode box
5–inside of the PIP dashboard (on the bottom half), click on Image, then the [+] button to add the desired image files from your computer
6–in the video window, you can resize the PIP image box
7–if you have added multiple images in PIP, double click on the image desired, and it will show that image

Bonus: Here are the ready-to-use Color Images

It's difficult to show color flags well during an online meeting. The following video shows two ways to show color flags more effectively.

1–using a webcam management software (like ManyCam or SplitCam) and without a green screen

2–using green screen and Zoom's virtual background function (many of the webcam software has similar function)

Additional Tips:
–Timers can add a bell along with the changing of the color flags
–Speakers can pin the Timers' screen (when using Zoom or Ring Central)
–Adding the words “Green/Yellow/Red” to the signs will help, even when colors are not shown properly