Yes, both Harvest and Slack offer a Free Trial.
Harvest is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Slack is designed for Freelancers, Large Enterprises, Medium Business and Small Business.
Pricing for Harvest Starts at $10.80/User/Month when Billed Yearly whereas for Slack Starts at $2.67/Month.
Some top alternatives to Harvest includes clockodo, Timesheets.com, TrackingTime, Clockify, TimeTrack, Time Track Bill, Timesheet, Hyperlogs, Timet and Time Tracker by eBillity.
Some top alternatives to Slack includes Microsoft Teams, Glip, Google Chat, ChatWork, Dialog, Office Chat, imBee, Takle, SPACE Channel and Teamwork Chat.