Have to agree with Copperbonnet - are there ANY employers who will tolerate sandals/flip-flops thereby ignoring the basics of Health & Safety in the workplace?
When I worked in local government sandals, anything open-toed, flip-flops, skyscraper stilletoes and especially platform footwear was absolutely no, no, no!
I've only worked for employers who will tolerate sandals and flip flops! In creative companies it's pretty standard to have zero rules and restrictions around clothing and footwear - just an expectation that if going on site to clients' offices for meetings that you will be presentable (but don't necessarily have to conform to the client company dress code)
Anything goes - you're not doing manual labour or working with hazardous chemicals, so you can wear what you like for sitting at a desk or standing at a whiteboard!
The CEO in my company is wearing jeans, flip flops and a t-shirt today
Another member of the C-suite is wearing open toed sandals, jeans and a sleeveless top (with her full sleeve, upper back and upper chest tattoos on display)
It's the quality of your work, not the clothes you wear, that count