From Glasgow, you can reach the island easily within 3 or 3.5 hours. The drive to Oban takes about 2 hours and goes along Loch Lomond on the A82 and then via Crianlarich, or you can carry on at Tarbet and follow the A83 via Inverary. Either way, the scenery is stunning. It then takes 40 minutes or so from Oban to reach the ferry at Cuan on the west of Seil, via the famous little ‘Bridge over the Atlantic’ at Clachan. The ferry goes every 30 minutes but for most of the year there is no car ferry on Sundays, only a foot ferry. During June, July and August, however, the car ferry runs until 10.30 p.m. Timetables may be viewed on the Calmac website.
There are trains to Oban from Glasgow but you would either need to hire a car in Oban or a taxi to take you to the island or the ferry terminal at Cuan.
Fly to Glasgow or Edinburgh Airport from which you can hire a car to take you to the island.