We start from the bottom:
There's only one 2-letter word LA, so it goes at the very bottom middle. Then there's only one 5-letter word with L in the middle, so STLKF goes there. We can rapidly fill in around that to get to here:
Now consider the 3-letter words beginning with P.
If it's PIA, then the 4-letter word ending with I must be PREI, but there are no 5-letter words ending with P. So it's PCB and then AADC, and then we can rapidly fill in NTB, DTE, DIE, AANG, AGE, and there are only two 5-letter words ending with A which share the same penultimate letter, so they must be DRAMA and OBAMA in some order.
Also from AGE there must be a 6-letter word beginning with A, whose fifth letter begins a 7-letter word, so that must be INDOSAT. Also the fourth letter of that 6-letter word must be A; it's also the fourth letter of a 5-letter word which must be ORMAS or ZAKAT, and the second letter of that is the fourth letter of a 6-letter word, so we can fill in ZAKAT, ZEN, TNI, NANTI, then ALBAIT and ASSAIA, then YENISEI going up and SOY.
Now in the top right we have limited possibilities:
The only 2-letter words with O in the middle are AON and SOY, but its first letter must be the last letter of a 7-letter word, so it's AON and WICHITA, then NEA, RTS, CHIEF, SWIPOA, FBI.
Two to the left of SWIPOA is another 6-letter word; its first letter is the second letter of either CPNSS or RAKSA, and its third letter is the second letter of either ANGIN or DUNIA. So we can fill in PIUDDR, CPNSS, DUNIA, SIA, CND, DUO, RUROUNI, and also ANGIN, MBA, LEM back on the right.
Now there's only two 6-letter words and two 7-letter words left (AOPMES, RIYALS and ABSENSI, OAKLAND), all over on the left-hand side and connected to each other. The only way we can do that is as follows:
Now there's lots of other stuff to be filled in around those long words on the left:
I need to go now, so I'm posting my progress so far and will come back to this an hour later to finish it