In a way that lacks skill or technical knowledge; with innocent sincerity without tricks or deception.
From artless (from art plus -less meaning 'without') plus -ly (adverb suffix). The underlying 'artless' means 'lacking art or skill' or 'innocent.'
What's fascinating is that 'artless' has two opposite meanings: it can mean both 'unskilled' and 'innocent/honest'—because deception is seen as an art form, lacking art can mean you're too honest to deceive!
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