It is hard to pronounce it as [æskt], and thus I hear it quite commonly pronounced as [æsd] as well. I am from the Northeast US. However, I have heard it pronounced both ways in media, which includes a variety of American accents. The thing is that [æsd] kind of sounds like a curse word and is frequently pronounced this way by African-Americans and Southerners and may be considered an inferior or less intelligent way to pronounce it. I find it often takes real effort to emphasize and make sure I pronounce and enunciate the "k" sound. Try forvo for a variety of pronunciations. Both are correct and natural. [æsd] may be frowned up by the snooty.

I'm not native to and not good at English, neither live in English-speaking countries, so I do not know the exact reality of the diversity of English pronunciation. But I'd like to hawk some ideas from books here. Successive two or three explosive consonants(stops) will make it awkward to enunciate each of them one after another, especially in fast speech. For English, people usually weaken or drop one or two stops in continuous speech, e.g. mortgage, looked, as long as it does not make difficulty or ambituity for understanding. As to words like asked, looked, the 'k' sound and 't' sound are respectively back and front stops, which makes it particularly difficult to pronounce them consecutively, and so there must be one to be left out. As the final 't' sound does matter: it indicates the meaning of past tense or past particle, therefor people weaken or drop the former stop 'k' sound. As classical and graceful pronunciation, you do not totally omit the 'k' sound, instead you make the articulation and keep it for a short time and then pronounce the next sound. But in causal and fast speech, the 'k' sound may be completely dropped. In everyday English, there would be even more sounds or sound groups be elided, which often causes difficulties for English learners to make out the words and to comprehend the phrases and sentences.

Don't worry, you aren't the only one who has trouble with this! I know a lot of native English people who mispronounce the root of this word - ask, pronouncing it as arx. Unforunately, when someone says 'arx' it marks them out as poorly educated/lower class. So do try and learn to pronounce this word correctly. Sorry I can't give you any helpful advice on excactly HOW to do that. (For such a little word, this one does cause a lot of trouble!)

You are right that it is difficult to pronounce all three consonants at the end of this word, and in fact many native speakers also miss out the 'k' sound. However, it's important to realise that the 'd' sound is not actually pronounced as a 'd'. It would sound strange to say /æsd/. The final consonant is actually a /t/ sound, as you can see from the dictionary transcription /æskt/. If you are speaking carefully, you would pronounce all three final consonants. Otherwise, it is fine to miss out the middle one. This produces the more relaxed pronunciation /æst/. The vowel sound may vary according to the regional pronunciation. For example, in standard British English, the pronunciation is /a:skt/ in the full form and /a:st/ in the more relaxed version. However, the consonant is the same, whatever your accent is. It ends in a /t/.

It depends on where you're from and I suppose it's really hard to explain a pronunciation to someone because depend on where you're from, you will interpret the pronunciation explanation differently. You're better off typing it into Forvo and checking the pronunciation types from different countries.