I suppose you could try to think of a separable verb that way, but it may sometimes lead you astray. Separable verbs are found in all Germanic languages, and really they function like prefixes in Slavic or some other features in other languages that are essential parts of verbs. Take the English verb "to make up," in this sense a synonym for "to imagine." If I make a new plan up based on the failure of the old one, is my plan now up in some way? Not really, especially since I could say I formulated a new plan or I imagined a new plan. I must admit that I often think of it the same way you do, though, when I am unfamiliar with the verb.
For me (a native English speaker) separable verbs largely fell into place in my mind when I recognized that we also have them in English but just rarely join them into one word.
Write down (a name), write up (a report), write off (a debt), knock off (work), hold up (an activity or a bank), look up (a phone number), fill in (your address), cross off (a list item), wind up (a clock or a business), figure out (a problem), pick up and drop off (a delivery), throw away (the garbage), fire up (an engine or a crowd), cut off (a conversation), give in (to an opponent), work out (a disagreement), show off (a skill), log on (a computer). But also underwrite (an insurance policy), overtake (a car on the highway), outspend (a market competitor), offload (cargo), overdub (a recording), etc.
There remains the tricky part in placement. And, by the way, that goes for English, too. You can "look it up," but you can't "look up it." Conversely, you can "get over it," but you can't "get it over." (I find it comforting to remind myself how difficult English is whenever I run into problems with another language.)