I’ve started introducing my daughter to phonics today. She too can spell out many letters (but I can’t test her, she says anything silly if i do, so I keep an eye on her and have heard which letters she’s spelled out loud)
I think it’s a good age as she still sees many whole words, is in love with her letters (like many 12-24mo on this forum and it would be fun to combine them. I think it’ll help with her speaking as well.
You can try playing with letter blocks and randomly put two letter blocks together. That’s how I knew Felicity could sound out new words even though I hadn’t taught her phonics then.