I'm sure Luc could step in and crush me with his decade of trader experience, but a "true" base requires a bounce and some volume. I see you're looking at amp here, but what we can't see is the numbers to see the actual % of that bounce. Was it a 12% bounce from the bottom of the stick? That's not bad.
Ignoring if the chart will/did eventually bounce back to the level at the first part of the chart, and just considering if where you put the yellow line is your base, I think a few key questions come out of this:
If a candlestick has a realllllly long lower shadow (the line below the body of the stick), is the bottom of that shadow where we start our base?
What kind of bounce, % wise, at minimum, are we looking at before we are calling things bases. 5%? 12%?
I'm sure Luc has this down in his brain as second nature, but how far beyond the base do you start buying in? Should we be afraid of buying at the top of the "safe zone" (thanks for the new term, Luc). This question kind of answers itself because there are generally (except in the case of really bad news) 2 outcomes:
1 - the price finds resistance slightly below the base and doesn't break, but you read it as a break, and you buy in, but the price goes up and you make money.
2 - the price does break and you end up buying more in down in the drop, and should only about break even with what you bought at the top of the "safe zone", but made money on what you bought throughout it.
What's nice about both of these outcomes? You make money every time.
As for questions 1 and 2, Luc may have some insight, but it may simple just be a feel for the market and experience. Was the bounce decent, but volume was enough to justify it being a base? The answer to those questions might just be trader nuance and not hard rules.