Experience practicing confrontation and boundaries?

I've just been thinking lately how I've had problems lately verbalizing my boundaries and I'm so anxious about confrontation I don't even say when something is bothering me so it just bottles up and festers inside me... does anyone have good strategies for coping with this or how to deal with it? Especially now since we've been stuck social distancing for so long? I want to "practice" so I can get more comfortable with it, but... idk how