Some conference call system will actually warn you when there is an echo on the line. Maybe the volume of your speakers is set too high and your microphone captures the sound of your speakers. This could create an echo.
Avoid echo, echo, echo. It doesn’t really sound professional. Check the settings of the conference call system that you are using.
Arrange for the correct sound settings. Have a test call to hear back how your voice to see if you are happy with the sound quality.
Add fabric in the room to avoid echo, reverb. Unless you want to sound like being in a large empty room. It could add to the effect of your conference call speech if that is an effect that you want to accomplish.