Is there a word that means simple but not easy? [duplicate]

Often I find myself or others describing a concept that is simple to explain, but difficult to execute. I end up saying "it's really simple, just not easy" way too often for my tastes. Is there a word that expresses this idea well?

Something that is simple to explain, but difficult to execute can be called tricky.

M-W:

tricky adjective

2 a : giving a deceptive impression of easiness, simplicity, or order : ticklish : a tricky path through the swamp

One word that may be suitable is awkward.

awkward [adjective]
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difficult to use, do, or deal with:

• It's an awkward corner, so take it slowly.