There are a couple of possible starting points to this hill. There is room for one (two at a squeeze) car at G37605 16401 A beside a faded signpost. From here proceed south for about 250m through rough heather/reeds before turning SW up the grassy/steepish slope next to a small stream for 1.5km. The summit is a broadest area marked with a large cairn surrounding a trig pillar. Fine views in all directions.
An alternative if the first parking spot is taken is to proceed NW along the road for approx 800m to a second parking spot at G37051 17039 B. From there head SW, again through heather initially then shortish grass & rocks up a steep but manageable incline passing between Lough Alone & another tiny pond to attain the summit. Up and down allow 1.5 hours. Linkback: https://mountainviews.ie/summit/753/comment/5512/

Started the walk at the 'Welcome To Mayo' sign G376 164 C where there is just room to park on a side road. Followed part of a path beside the sign and information rock before turning left uphill. There are a number of sheep trails and tracks to follow, I only found them on the way down, which seems to suggest it's a popular climb despite the low usage on MountainViews. There is a little gully and stream ( used as the Sligo/Mayo border line) which I followed up to near the top where it levels off to give magnificent views of Lough Talt on one side, and the Nephins on the other.The trig itself is almost buried beneath the summit cairn. Give it about an hour up and down. Well worth a visit. Linkback: https://mountainviews.ie/summit/753/comment/6705/

You may feel that I am ill qualified to comment at all on Knocknasliggaun since I have not yet been to its peak. In fact I have been up what is probably the best part of the mountain which hangs majestically over Lough Talt, one of County Mayo's hidden gems. The Lough can be found on the road from Ballina to Tobercurry, about mid way. I approached from the eastern tip of the lake and took the road that runs along the south of the lake to the base of the mountain. There's plenty of parking. I did a full circuit of the lake same years ago taking in part of Knocknasliggaun but the rest of the walk was at "ground level". I would highly recommend this area. A great combination of mountain and lake. Linkback: https://mountainviews.ie/summit/753/comment/17748/

View of Lough Talt in the Ox Mountains Linkback: https://mountainviews.ie/summit/753/comment/19984/

Started at G376 164 C at the information sign too. Parked
on a side road opposite it where the road widened to leave space. Followed the wee stream and fence beside it straight up the hill keeping between the stream and fence. At approx point
G373 158 D turn up the hill in a south/south west direction where the summit trig and cairn will be visible within a few hundred metres. Really lovely views from on top of Lough Alone and Lough Corskea and out to Ballina and Enniscrone and the Atlantic ocean. Linkback: https://mountainviews.ie/summit/753/comment/23161/

Although there are fine views from the summit area, one that isn't visible from the cairn is that overlooking Lough Talt, so I heartily recommend that your make a minor detour about 200m NWW from the cairn to G373 157 E where you are presented with a magnificent view of the sizeable lough and surrounding landscape. Linkback: https://mountainviews.ie/summit/753/comment/23499/